Coincidence time resolution optimization method and device

Abstract

The invention provides a coincidence time resolution optimization method and device. The method comprises the following steps: amplifying fast output pulse signals of a first PET probe and a second PET probe by using an amplifier; determining the first pulse arrival time and the second pulse arrival time of the first PET probe and the first pulse arrival time and the second pulse arrival time of the second PET probe by using a first preset voltage threshold value and a second preset voltage threshold value; determining a first time difference between the first pulse arrival time of the first PET probe and the second pulse arrival time of the second PET probe and a second time difference between the second pulse arrival time of the first PET probe and the second PET probe; according to the first time difference and the second time difference, the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe is determined, and the CTR is determined according to the final pulse arrival time difference. According to the invention, more accurate pulse time difference of arrival can be obtained, so that the accuracy of CTR is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of PET (Positron Emission Tomography) detectors, and in particular to a method and device for optimizing time resolution. Background Art

[0002] Currently, there are two common methods for determining CTR (Coincidence Time Resolution) in readout electronics, namely Leading Edge Discriminator (LED) and Constant Fraction Discriminator (CFD).

[0003] The LED method uses only the rising edge of the pulse to determine its arrival time when the pulse triggers a certain voltage threshold. However, this method will produce a time walk effect (TimeWalk) when facing pulses with a relatively slow rise speed and a large range of pulse amplitude variations, which greatly affects the accuracy of time information extraction. To alleviate this problem, the current mainstream method is to use an energy-based filter, and it is best to use a low threshold when extracting time information. But in fact, in actual circuits, noise will be triggered by a threshold that is too low, affecting the accuracy of time information.

[0004] The CFD method uses the method of delaying and subtracting the waveform after attenuation, and there is no time wandering problem. However, CFD requires a lot of calibration in hardware and software to maximize the effectiveness of this method, which is very difficult in terms of engineering application costs. Therefore, in engineering applications, a more effective method is based on the LED method, which needs to try to solve or reduce the impact of the time wandering problem on time accuracy. Summary of the invention

[0005] The present invention provides a method and device for optimizing time resolution, which are used to solve the defect that the LED method in the prior art is affected by the time wandering effect and cannot accurately determine the pulse arrival time of each PET probe, thereby causing the pulse arrival time difference of two PET probes to be inaccurate and affecting the accuracy of CTR, so as to obtain a more accurate pulse arrival time difference and improve the accuracy of CTR.

[0006] The present invention provides a method for optimizing time resolution, comprising:

[0007] amplifying the fast output pulse signals of the first PET probe and the second PET probe using an amplifier;

[0008] The time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold is respectively used as the first pulse arrival time and the second pulse arrival time of the first PET probe, and the first preset voltage threshold is less than the second preset voltage threshold;

[0009] The time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold is used as the first pulse arrival time and the second pulse arrival time of the second PET probe respectively;

[0010] determining a first time difference between arrival times of a first pulse of the first PET probe and the second PET probe, and a second time difference between arrival times of a second pulse of the first PET probe and the second PET probe;

[0011] The final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe is determined according to the first time difference and the second time difference, and the compliance time resolution is determined according to the final pulse arrival time difference.

[0012] According to a time resolution optimization method provided by the present invention, determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference includes:

[0013] In the case where the rising edges of the amplified fast output pulse signals of the first PET probe and the second PET probe are not completely parallel, determining the degree to which the rising edges are not completely parallel;

[0014] In a case where the degree to which the rising edges are not completely parallel is greater than a preset degree threshold, the final pulse arrival time difference is determined according to the first time difference or the second time difference.

[0015] In a case where the degree to which the rising edges are not completely parallel is less than or equal to the preset degree threshold, the final pulse arrival time difference is determined according to the first time difference and the second time difference.

[0016] According to a time resolution optimization method provided by the present invention, the degree to which the rising edges are not completely parallel is the ratio of the first time difference to the second time difference.

[0017] According to a time resolution optimization method provided by the present invention, when the degree to which the rising edges are not completely parallel is less than or equal to the preset degree threshold, determining the final pulse arrival time difference according to the first time difference and the second time difference, comprising:

[0018] When the degree to which the rising edges are not completely parallel is less than or equal to the preset degree threshold, comparing the second time difference with the first time difference;

[0019] When the second time difference is greater than the first time difference, scaling the fast output pulse signal of the first PET probe or the second PET probe based on an energy normalization method;

[0020] Based on the scaled fast output pulse signal, updating the first time difference and the second time difference;

[0021] The final pulse arrival time difference is determined according to the updated first time difference and the updated second time difference.

[0022] According to a time resolution optimization method provided by the present invention, determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference includes:

[0023] When the rising edges of the amplified fast output pulse signals of the first PET probe and the second PET probe intersect, the final pulse arrival time difference is determined according to the first time difference and the second time difference.

[0024] According to a time resolution optimization method provided by the present invention, determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference includes:

[0025] determining a third time difference between a first pulse arrival time and a second pulse arrival time of the first PET probe, and a fourth time difference between the first pulse arrival time and the second pulse arrival time of the second PET probe;

[0026] determining a fifth time difference between the first time difference and the second time difference, and a sixth time difference between the third time difference and the fourth time difference;

[0027] determining whether the fast output pulse signals of the first PET probe and the second PET probe are simultaneous events according to one or more of the first time difference, the second time difference, the third time difference, the fourth time difference, the fifth time difference, and the sixth time difference;

[0028] In the case of determining that it is a simultaneous event, a final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe is determined according to the first time difference and the second time difference.

[0029] According to a time resolution optimization method provided by the present invention, determining a first time difference between a first pulse arrival time of the first PET probe and a first pulse arrival time of the second PET probe, and a second time difference between a second pulse arrival time of the first PET probe and a second PET probe comprises:

[0030] amplifying the standard output pulse signals of the first PET probe and the second PET probe using the amplifier;

[0031] The time when the rising edge of the standard output pulse signal amplified by the first PET probe and the second PET probe exceeds the third preset voltage threshold is respectively used as the third pulse arrival time of the first PET probe and the second PET probe;

[0032] determining a seventh time difference between arrival times of third pulses of the first PET probe and the second PET probe;

[0033] Using the seventh time difference to perform an offset process on the first pulse arrival time and the second pulse arrival time of the first PET probe, or to perform an offset process on the first pulse arrival time and the second pulse arrival time of the second PET probe;

[0034] A first time difference between arrival times of first pulses of the first PET probe and the second PET probe after the offset processing and a second time difference between arrival times of second pulses of the first PET probe and the second PET probe after the offset processing are determined.

[0035] According to a time resolution optimization method provided by the present invention, determining whether the fast output pulse signals of the first PET probe and the second PET probe are simultaneous events according to one or more of the first time difference, the second time difference, the third time difference, the fourth time difference, the fifth time difference and the sixth time difference includes:

[0036] respectively determining a first pulse arrival time and a second pulse arrival time of the first PET probe, and an absolute value of an eighth time difference between the first pulse arrival time and the second pulse arrival time of the second PET probe and a third pulse arrival time of the first PET probe;

[0037] respectively determining a first pulse arrival time and a second pulse arrival time of the first PET probe, and an absolute value of a ninth time difference between the first pulse arrival time and the second pulse arrival time of the second PET probe and a third pulse arrival time of the second PET probe;

[0038] determining whether the fast output pulse signals of the first PET probe and the second PET probe are true events according to whether the absolute value of the eighth time difference and the absolute value of the ninth time difference exceed a preset safety threshold;

[0039] When it is determined to be a true event, it is determined whether the fast output pulse signals of the first PET probe and the second PET probe are simultaneous events based on one or more of the first time difference, the second time difference, the third time difference, the fourth time difference, the fifth time difference and the sixth time difference.

[0040] The present invention also provides a device for optimizing time resolution, comprising:

[0041] an amplification module, used to amplify the fast output pulse signals of the first PET probe and the second PET probe using an amplifier;

[0042] a first extraction module, configured to use the time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds a first preset voltage threshold and a second preset voltage threshold as a first pulse arrival time and a second pulse arrival time of the first PET probe, respectively, and the first preset voltage threshold is less than the second preset voltage threshold;

[0043] a second extraction module, taking the time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold as the first pulse arrival time and the second pulse arrival time of the second PET probe, respectively;

[0044] a calculation module, configured to determine a first time difference between arrival times of first pulses of the first PET probe and the second PET probe, and a second time difference between arrival times of second pulses of the first PET probe and the second PET probe;

[0045] The optimization module is used to determine the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference, and determine the time resolution according to the final pulse arrival time difference.

[0046] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, a method for optimizing time resolution as described above is implemented.

[0047] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any of the above-described time resolution optimization methods.

[0048] The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the time-resolution optimization method described above is implemented.

[0049] The time resolution optimization method and device provided by the present invention increase the amplitude of the pulse while maintaining the pulse width unchanged by adopting the method of amplifying the pulse, thereby obtaining a steeper rising edge, thereby reducing the impact of the time wandering problem; the final pulse arrival time difference is determined based on the time difference obtained from two preset voltage thresholds, so that a more accurate pulse arrival time difference can be obtained, and more information can be introduced to determine simultaneous events, thereby improving the accuracy of CTR. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 It is a schematic diagram of a flow chart of a method for optimizing time resolution provided by the present invention;

[0052] Figure 2 This is a schematic diagram of amplifying a standard output pulse signal in a time resolution optimization method provided by the present invention;

[0053] Figure 3 This is a schematic diagram of amplifying a fast output pulse signal in a time resolution optimization method provided by the present invention;

[0054] Figure 4 It is a schematic diagram of the structure of the device for optimizing time resolution provided by the present invention;

[0055] Figure 5 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] Positron emission tomography (PET) is an imaging technology that can display the metabolic level of living biological molecules and the activity of neurotransmitters. Due to its extremely high sensitivity, it plays an irreplaceable role in the diagnosis and research of various diseases. The PET probe is a crucial part of the PET instrument. It consists of a scintillation crystal and a silicon photomultiplier (SiPM). The gamma photon is deposited inside the crystal, and the visible light photon is emitted and then received by the SiPM. SiPM is a solid-state high-gain radiation detector. The sensor based on the PN junction has single-photon sensitivity and generates an output current pulse after absorbing the photon. The time information of the gamma photon deposition in the detector can be obtained from it. The accuracy of the time information is the key to improving the imaging quality, spatial resolution, and system sensitivity in subsequent processing. Therefore, how to obtain more accurate and higher time resolution is the key point of current research.

[0058] Combine the following Figure 1 A method for optimizing time resolution according to the present invention is described, comprising:

[0059] Step 101, using an amplifier to amplify the fast output pulse signals of the first PET probe and the second PET probe;

[0060] CTR is obtained by coincidence events. A coincidence event is determined when two signals with almost the same energy are detected within a certain time window. In this particular event in PET, two oppositely directed gamma photons with the same energy are generated during the positron annihilation process. These two gamma photons then deposit their energy in two scintillators in the line of response (LOR) between the first PET probe and the second PET probe and become a light signal. Finally, the light signal is converted into an electrical scintillation pulse. The time difference between these two scintillation pulses determines the CTR. The higher the CTR, the smaller the uncertainty in obtaining the positron position information, and therefore the better the imaging performance.

[0061] The fast output pulse signal fastout of the first PET probe and the second PET probe can be output by the fast output channel of the SiPM in the first PET probe and the second PET probe, or the output of the standard output channel of the SiPM in the first PET probe and the second PET probe can be obtained through a differential circuit. The differential circuit can adopt active differentiation or passive differentiation.

[0062] This embodiment proposes a signal processing technology pipeline implemented in a readout electronic device to improve CTR. First, an amplifier is introduced at the front end of the readout electronic device. The amplifier can be a low noise amplifier (LowNoiseAmplifier, LNA) or other hardware with amplification function. Adding an amplifier here is equivalent to lowering the effective voltage threshold. Assuming that the amplifier has an amplification factor of A, the equivalent voltage threshold will be reduced by A times, so the time wander problem can be significantly alleviated, thereby possibly improving CTR.

[0063] Step 102, taking the time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold as the first pulse arrival time and the second pulse arrival time of the first PET probe, respectively, and the first preset voltage threshold is less than the second preset voltage threshold;

[0064] Step 103, taking the time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold as the first pulse arrival time and the second pulse arrival time of the second PET probe respectively;

[0065] refer to Figure 2 and Figure 3 It can be seen that adding an amplifier can not only amplify the useful signal, but also amplify the noise. More specifically, under the amplification of the amplifier or op amp circuit, not only the baseline noise will be amplified, but the noise of the components will also be introduced into the pulse signal. On the other hand, the differential of the effective scintillation pulse usually has an amplitude of about 60mV. With this scintillation pulse as input, the output of the amplifier is saturated and the signal is seriously distorted.

[0066] In view of the noise problem, this embodiment proposes a dual-threshold LED technology. The time information obtained at the lower threshold (the first preset voltage threshold) is used to obtain the accurate trigger time in a timely manner when the time wandering is small. The LED at the other higher threshold (the second preset voltage threshold) position is used to help correctly identify the qualified trigger time in the case of severe noise.

[0067] Step 104, determining a first time difference between arrival times of first pulses of the first PET probe and the second PET probe, and a second time difference between arrival times of second pulses of the first PET probe and the second PET probe;

[0068] Determine the time difference corresponding to the two voltage thresholds, ie, the first time difference and the second time difference.

[0069] Step 105, determining a final pulse arrival time difference between fast output pulse signals of the first PET probe and the second PET probe based on the first time difference and the second time difference, and determining compliance with time resolution based on the final pulse arrival time difference.

[0070] The average or weighted sum of the first time difference and the second time difference can be used as the final pulse arrival time difference. Whether the fast output pulse signals of the two PET probes are a coincidence event can be determined based on the first time difference and the second time difference. If both the first time difference and the second time difference are less than the set value, it is determined to be a coincidence event. More information can be introduced to determine the coincidence event, and a more accurate pulse arrival time difference can be obtained.

[0071] The first time difference and the second time difference may also be compared, and the final pulse arrival time difference may be determined based on the comparison result. For example, when the difference between the first time difference and the second time difference is less than a set value, the average value or weighted sum of the first time difference and the second time difference may be used as the final pulse arrival time difference. When the difference between the first time difference and the second time difference is greater than or equal to the set value, the second time difference may be used as the final pulse arrival time difference. This embodiment does not limit the method for determining the final pulse arrival time difference based on the first time difference and the second time difference.

[0072] The final pulse arrival time difference is fitted, and the CTR can be calculated based on the fitting curve. Through hardware and software processing, the accuracy of CTR is greatly improved.

[0073] This embodiment adopts the method of amplifying the pulse to increase its amplitude while maintaining the pulse width unchanged, thereby obtaining a steeper rising edge, thereby reducing the impact of the time wandering problem; the final pulse arrival time difference is determined based on the time difference obtained based on two preset voltage thresholds, so as to obtain a more accurate pulse arrival time difference, thereby improving the accuracy of CTR.

[0074] Based on the above embodiment, the method of determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference in this embodiment includes:

[0075] In the case where the rising edges of the amplified fast output pulse signals of the first PET probe and the second PET probe are not completely parallel, determining the degree to which the rising edges are not completely parallel;

[0076] In a case where the degree to which the rising edges are not completely parallel is greater than a preset degree threshold, the final pulse arrival time difference is determined according to the first time difference or the second time difference.

[0077] In a case where the degree to which the rising edges are not completely parallel is less than or equal to the preset degree threshold, the final pulse arrival time difference is determined according to the first time difference and the second time difference.

[0078] Assume that the first pulse arrival time and the second pulse arrival time of the first PET probe are and The first pulse arrival time and the second pulse arrival time of the second PET probe are and exist When , it can be determined that the rising edges of the amplified fast output pulse signals of the first PET probe and the second PET probe are completely parallel; When the first PET probe and the second PET probe amplified fast output pulse signal are not completely parallel, it can be determined that the rising edges of the amplified fast output pulse signal are not completely parallel, and the degree of the incomplete parallelism of the rising edges is further determined. The greater the difference between the first time difference and the second time difference, the greater the degree of incomplete parallelism. This embodiment does not limit the calculation method of the degree of incomplete parallelism.

[0079] When the degree of incomplete parallelism is serious, it is necessary to remove abnormal values, such as values ​​that are too large, and retain the more reasonable value. When the degree of incomplete parallelism is weak, it can be approximately considered that the rising edges of the two pulses are parallel, so an average value of the two time differences can be taken to further reduce instability.

[0080] This embodiment classifies the time differences obtained by two preset voltage thresholds to obtain a more accurate arrival time difference, thereby improving the accuracy of the CTR.

[0081] On the basis of the above embodiment, in this embodiment, the degree to which the rising edges are not completely parallel is the ratio of the first time difference to the second time difference.

[0082] The final pulse arrival time difference is calculated as follows:

[0083]

[0084] Δt is the final pulse arrival time difference, λ is the preset degree threshold, λ can be set according to the actual situation, and the possible value is 2.

[0085] On the basis of the above embodiment, in this embodiment, when the degree to which the rising edges are not completely parallel is less than or equal to the preset degree threshold, determining the final pulse arrival time difference according to the first time difference and the second time difference includes:

[0086] When the degree to which the rising edges are not completely parallel is less than or equal to the preset degree threshold, comparing the second time difference with the first time difference;

[0087] When the second time difference is greater than the first time difference, scaling the fast output pulse signal of the first PET probe or the second PET probe based on an energy normalization method;

[0088] Based on the scaled fast output pulse signal, updating the first time difference and the second time difference;

[0089] The final pulse arrival time difference is determined according to the updated first time difference and the updated second time difference.

[0090] When the second time difference is greater than the first time difference, that is, the upper part is larger and the lower part is smaller, it can be considered to compress or expand the pulse root based on the energy normalization method to obtain a new fast output pulse signal.

[0091] Assume that the energies of the fast output pulse signals of the first PET probe and the second PET probe are E L and E R The fast output pulse signal of the second PET probe can be adjusted according to E L / E R The scaling can be achieved by using the peak value of the fast output pulse signal, because the energy is proportional to the pulse peak value. The first pulse arrival time and the second pulse arrival time of the second PET probe are recalculated using the scaled fast output pulse signal of the second PET probe as follows: and The final pulse arrival time difference is calculated as follows:

[0092]

[0093] Based on the above embodiment, the method of determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference in this embodiment includes:

[0094] When the rising edges of the amplified fast output pulse signals of the first PET probe and the second PET probe intersect, the final pulse arrival time difference is determined according to the first time difference and the second time difference.

[0095] exist In the case of , the rising edge crossing of the fast output pulse signal can be determined. The calculation formula for the final pulse arrival time difference is as follows:

[0096]

[0097] Based on the above embodiments, the method of determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference in this embodiment includes:

[0098] determining a third time difference between a first pulse arrival time and a second pulse arrival time of the first PET probe, and a fourth time difference between the first pulse arrival time and the second pulse arrival time of the second PET probe;

[0099] determining a fifth time difference between the first time difference and the second time difference, and a sixth time difference between the third time difference and the fourth time difference;

[0100] determining whether the fast output pulse signals of the first PET probe and the second PET probe are simultaneous events according to one or more of the first time difference, the second time difference, the third time difference, the fourth time difference, the fifth time difference, and the sixth time difference;

[0101] In the case of determining that it is a simultaneous event, a final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe is determined according to the first time difference and the second time difference.

[0102] In simultaneous events, one flash pulse should be a delayed copy of the other. If the trigger time is sampled at the rising edge, the time difference between the two pulses should be independent of threshold variations if the energy of the two pulses is the same and an LED is used. Therefore, if multiple thresholds are used, the time difference obtained from each threshold should also be within a tolerable window, taking into account energy loss, thereby filtering out distorted outliers.

[0103] The traditional judgment strategy will be affected by ground noise, and this special situation cannot be solved simply by increasing the threshold voltage. In order to solve this problem, this embodiment not only uses time (such as the first time difference, the second time difference and the fifth time difference), but also uses the shape of the pulse (such as the third time difference, the fourth time difference and the sixth time difference) to determine the simultaneous events. The specific formula for determining the simultaneous time is as follows:

[0104]

[0105] The above conditions need to be met at the same time, t' e , t' e 'and t' e " is the set value.

[0106] This embodiment can introduce more information to judge simultaneous events by classifying the time difference obtained by two preset voltage thresholds, thereby obtaining a more accurate arrival time difference; judging and processing by the difference of the time information of a pair of pulses, rather than the several time information of a single pulse itself, this processing method can greatly reduce the amount of calculation required for the code processing process through the mutual verification of the information of the two pairs of pulses. In addition, by reading out the waveform, energy information and time information separately, more accurate time and energy information can be obtained.

[0107] Based on the above embodiment, in this embodiment, determining a first time difference between arrival times of first pulses of the first PET probe and the second PET probe, and a second time difference between arrival times of second pulses of the first PET probe and the second PET probe includes:

[0108] Amplifying the standard output pulse signal standout of the first PET probe and the second PET probe using the amplifier;

[0109] The time when the rising edge of the standard output pulse signal amplified by the first PET probe and the second PET probe exceeds the third preset voltage threshold is respectively used as the third pulse arrival time of the first PET probe and the second PET probe and

[0110] Determine a seventh time difference t between the third pulse arrival times of the first PET probe and the second PET probe b ;

[0111] The first pulse arrival time of the first PET probe is calculated using the seventh time difference and the second pulse arrival time After offset processing, we get and Alternatively, the first pulse arrival time of the second PET probe and the second pulse arrival time After offset processing, we get and

[0112] Determine the first pulse arrival time after the first PET probe and the second PET probe are offset and a first time difference between the first PET probe and the second PET probe, and a second pulse arrival time after the offset processing between the first PET probe and the second PET probe and The second time difference between.

[0113] On the basis of the above embodiment, in this embodiment, determining whether the fast output pulse signals of the first PET probe and the second PET probe are simultaneous events according to one or more of the first time difference, the second time difference, the third time difference, the fourth time difference, the fifth time difference and the sixth time difference includes:

[0114] respectively determining a first pulse arrival time and a second pulse arrival time of the first PET probe, and an absolute value of an eighth time difference between the first pulse arrival time and the second pulse arrival time of the second PET probe and a third pulse arrival time of the first PET probe;

[0115] respectively determining a first pulse arrival time and a second pulse arrival time of the first PET probe, and an absolute value of a ninth time difference between the first pulse arrival time and the second pulse arrival time of the second PET probe and a third pulse arrival time of the second PET probe;

[0116] determining whether the fast output pulse signals of the first PET probe and the second PET probe are true events according to whether the absolute value of the eighth time difference and the absolute value of the ninth time difference exceed a preset safety threshold;

[0117] When it is determined to be a true event, it is determined whether the fast output pulse signals of the first PET probe and the second PET probe are simultaneous events based on one or more of the first time difference, the second time difference, the third time difference, the fourth time difference, the fifth time difference and the sixth time difference.

[0118] Determine whether the difference between the sampling points of the fast output pulse signal and the standard output pulse signal exceeds the safety threshold, ensuring that the fast output pulse signals of the first PET probe and the second PET probe are a pair of true coincidence events, rather than false events triggered by mistake. The safety threshold can be set according to the characteristic pulse length emitted by the radiation source. A true event must meet the following conditions:

[0119]

[0120] Among them, t e The preset safety threshold.

[0121] Existing LED technology is affected by the time walk effect and the position noise near the baseline, and performs poorly in determining pulse arrival time information and judging coincidence events. This embodiment uses pulse amplification and multi-threshold methods in hardware, and classifies the time difference obtained by two thresholds in the algorithm, which can introduce more information to judge coincidence events and obtain more accurate arrival time differences.

[0122] CFD technology requires delay and attenuation before subtraction, which is very difficult and costly to apply in both hardware and software, and is not conducive to subsequent large-scale integration in PET systems. This embodiment is an improvement based on the LED method, which not only maintains the characteristics of simple circuit implementation, but also adds the advantage of obtaining more accurate time information.

[0123] The TOT method has the advantages of simplicity, low cost and power efficiency, and can record the energy and timing information required by the TOF-PET scanner. However, they are affected by the nonlinear relationship between the pulse width and the energy deposited in the detector. Therefore, in its specific use, a higher threshold setting is usually adopted, thereby improving linearity at the expense of a smaller signal dynamic range. Therefore, the TOT method needs to make a trade-off between simplicity and achievable energy performance, and too high a threshold selection will greatly increase the impact of the time wandering effect. This embodiment adopts a method of separately acquiring and calculating energy and time, and adopts a fastout signal (differential signal of the standard output) in the time part, which is the part of the high-frequency signal in the standard pulse output, and it has a shorter rise time and a steeper rising edge, which can reduce the impact of time wandering from the pulse itself and obtain accurate time information.

[0124] The time-resolution optimization device provided by the present invention is described below. The time-resolution optimization device described below and the time-resolution optimization method described above can be referenced to each other.

[0125] like Figure 4 As shown, the device includes an amplification module 401, a first extraction module 402, a second extraction module 403, a calculation module 404 and an optimization module 405, wherein:

[0126] The amplification module 401 is used to amplify the fast output pulse signals of the first PET probe and the second PET probe using an amplifier;

[0127] The first extraction module 402 is used to use the time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold as the first pulse arrival time and the second pulse arrival time of the first PET probe, respectively, and the first preset voltage threshold is less than the second preset voltage threshold;

[0128] The second extraction module 403 is used to use the time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold as the first pulse arrival time and the second pulse arrival time of the second PET probe respectively;

[0129] The calculation module 404 is used to determine a first time difference between the arrival times of the first pulse of the first PET probe and the second PET probe, and a second time difference between the arrival times of the second pulse of the first PET probe and the second PET probe;

[0130] The optimization module 405 is used to determine the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference, and determine the time resolution according to the final pulse arrival time difference.

[0131] This embodiment adopts a pulse amplification method to increase the amplitude of the pulse while maintaining the pulse width unchanged, thereby obtaining a steeper rising edge, thereby reducing the impact of the time wandering problem; the final pulse arrival time difference is determined based on the time difference obtained based on two preset voltage thresholds, so that a more accurate pulse arrival time difference can be obtained, thereby improving the accuracy of CTR.

[0132] Figure 5 An example of a physical structure diagram of an electronic device is shown in FIG. Figure 5 As shown, the electronic device may include: a processor 510, a communication interface 520, a memory 530 and a communication bus 540, wherein the processor 510, the communication interface 520 and the memory 530 communicate with each other through the communication bus 540. The processor 510 may call the logic instructions in the memory 530 to execute the time resolution optimization method, which includes: using an amplifier to amplify the fast output pulse signals of the first PET probe and the second PET probe; using a first preset voltage threshold and a second preset voltage threshold to determine the first pulse arrival time and the second pulse arrival time of the first PET probe, and the first pulse arrival time and the second pulse arrival time of the second PET probe; determining the first time difference between the first pulse arrival time of the first PET probe and the second PET probe, and the second time difference between the second pulse arrival time; determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference, and determining the CTR according to the final pulse arrival time difference.

[0133] In addition, the logic instructions in the above-mentioned memory 530 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on such an understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0134] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the time resolution optimization method provided by the above methods, which includes: using an amplifier to amplify the fast output pulse signals of the first PET probe and the second PET probe; using a first preset voltage threshold and a second preset voltage threshold to determine the first pulse arrival time and the second pulse arrival time of the first PET probe, as well as the first pulse arrival time and the second pulse arrival time of the second PET probe; determining a first time difference between the first pulse arrival times of the first PET probe and the second PET probe, and a second time difference between the second pulse arrival times; determining a final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe based on the first time difference and the second time difference, and determining CTR based on the final pulse arrival time difference.

[0135] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which is implemented when the processor executes the time resolution optimization method provided by the above-mentioned methods, and the method includes: using an amplifier to amplify the fast output pulse signals of the first PET probe and the second PET probe; using a first preset voltage threshold and a second preset voltage threshold to determine the first pulse arrival time and the second pulse arrival time of the first PET probe, as well as the first pulse arrival time and the second pulse arrival time of the second PET probe; determining a first time difference between the first pulse arrival times of the first PET probe and the second PET probe, and a second time difference between the second pulse arrival times; determining a final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe based on the first time difference and the second time difference, and determining CTR based on the final pulse arrival time difference.

[0136] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0137] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for optimizing time resolution, characterized in that: include: amplifying the fast output pulse signals of the first PET probe and the second PET probe using an amplifier; The time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold is used as the first pulse arrival time and the second pulse arrival time of the first PET probe, respectively, and the first preset voltage threshold is less than the second preset voltage threshold; The time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold is used as the first pulse arrival time and the second pulse arrival time of the second PET probe respectively; Determining a first time difference between a first pulse arrival time of the first PET probe and a first pulse arrival time of the second PET probe, and a second time difference between a second pulse arrival time of the first PET probe and a second PET probe; The final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe is determined according to the first time difference and the second time difference, and the compliance time resolution is determined according to the final pulse arrival time difference.

2. The time resolution optimization method according to claim 1, characterized in that: Determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference includes: In the case where the rising edges of the amplified fast output pulse signals of the first PET probe and the second PET probe are not completely parallel, determining the degree to which the rising edges are not completely parallel; In a case where the degree to which the rising edges are not completely parallel is greater than a preset degree threshold, the final pulse arrival time difference is determined according to the first time difference or the second time difference. In a case where the degree to which the rising edges are not completely parallel is less than or equal to the preset degree threshold, the final pulse arrival time difference is determined according to the first time difference and the second time difference.

3. The time resolution optimization method according to claim 2, characterized in that: The degree to which the rising edges are not completely parallel is the ratio of the first time difference to the second time difference.

4. The method for optimizing the time resolution according to claim 2, characterized in that: In a case where the degree to which the rising edges are not completely parallel is less than or equal to the preset degree threshold, determining the final pulse arrival time difference according to the first time difference and the second time difference comprises: When the degree to which the rising edges are not completely parallel is less than or equal to the preset degree threshold, comparing the second time difference with the first time difference; When the second time difference is greater than the first time difference, scaling the fast output pulse signal of the first PET probe or the second PET probe based on an energy normalization method; Based on the scaled fast output pulse signal, updating the first time difference and the second time difference; The final pulse arrival time difference is determined according to the updated first time difference and the updated second time difference.

5. The time-resolution optimization method according to claim 1, characterized in that: Determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference includes: When the rising edges of the amplified fast output pulse signals of the first PET probe and the second PET probe intersect, the final pulse arrival time difference is determined according to the first time difference and the second time difference.

6. The method for optimizing time resolution according to any one of claims 1 to 5, characterized in that: Determining the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference includes: determining a third time difference between a first pulse arrival time and a second pulse arrival time of the first PET probe, and a fourth time difference between the first pulse arrival time and the second pulse arrival time of the second PET probe; determining a fifth time difference between the first time difference and the second time difference, and a sixth time difference between the third time difference and the fourth time difference; determining whether the fast output pulse signals of the first PET probe and the second PET probe are simultaneous events according to one or more of the first time difference, the second time difference, the third time difference, the fourth time difference, the fifth time difference, and the sixth time difference; In the case of determining that it is a simultaneous event, a final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe is determined according to the first time difference and the second time difference.

7. The time-resolution optimization method according to claim 6, characterized in that: Determining a first time difference between first pulse arrival times of the first PET probe and the second PET probe, and a second time difference between second pulse arrival times of the first PET probe and the second PET probe, comprises: amplifying the standard output pulse signals of the first PET probe and the second PET probe using the amplifier; The time when the rising edge of the standard output pulse signal amplified by the first PET probe and the second PET probe exceeds the third preset voltage threshold is respectively used as the third pulse arrival time of the first PET probe and the second PET probe; determining a seventh time difference between arrival times of third pulses of the first PET probe and the second PET probe; Using the seventh time difference to perform an offset process on the first pulse arrival time and the second pulse arrival time of the first PET probe, or to perform an offset process on the first pulse arrival time and the second pulse arrival time of the second PET probe; A first time difference between arrival times of first pulses of the first PET probe and the second PET probe after the offset processing and a second time difference between arrival times of second pulses of the first PET probe and the second PET probe after the offset processing are determined.

8. The time-resolution optimization method according to claim 7, characterized in that: Determining whether the fast output pulse signals of the first PET probe and the second PET probe are simultaneous events according to one or more of the first time difference, the second time difference, the third time difference, the fourth time difference, the fifth time difference, and the sixth time difference includes: respectively determining a first pulse arrival time and a second pulse arrival time of the first PET probe, and an absolute value of an eighth time difference between the first pulse arrival time and the second pulse arrival time of the second PET probe and a third pulse arrival time of the first PET probe; respectively determining a first pulse arrival time and a second pulse arrival time of the first PET probe, and an absolute value of a ninth time difference between the first pulse arrival time and the second pulse arrival time of the second PET probe and a third pulse arrival time of the second PET probe; determining whether the fast output pulse signals of the first PET probe and the second PET probe are true events according to whether the absolute value of the eighth time difference and the absolute value of the ninth time difference exceed a preset safety threshold; When it is determined to be a true event, it is determined whether the fast output pulse signals of the first PET probe and the second PET probe are simultaneous events based on one or more of the first time difference, the second time difference, the third time difference, the fourth time difference, the fifth time difference and the sixth time difference.

9. A device for optimizing time resolution, characterized in that: include: an amplification module, used to amplify the fast output pulse signals of the first PET probe and the second PET probe using an amplifier; a first extraction module, configured to use the time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds a first preset voltage threshold and a second preset voltage threshold as a first pulse arrival time and a second pulse arrival time of the first PET probe, respectively, and the first preset voltage threshold is less than the second preset voltage threshold; a second extraction module, configured to use the time when the rising edge of the fast output pulse signal amplified by the first PET probe exceeds the first preset voltage threshold and the second preset voltage threshold as the first pulse arrival time and the second pulse arrival time of the second PET probe, respectively; a calculation module, configured to determine a first time difference between arrival times of first pulses of the first PET probe and the second PET probe, and a second time difference between arrival times of second pulses of the first PET probe and the second PET probe; The optimization module is used to determine the final pulse arrival time difference between the fast output pulse signals of the first PET probe and the second PET probe according to the first time difference and the second time difference, and determine the time resolution according to the final pulse arrival time difference.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the time-resolution optimization method as described in any one of claims 1 to 8 is implemented.

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