阅读说明：本技术 Pet成像设备的堆积信号恢复方法、pet成像设备及计算机可读存储介质 (Stacking signal recovery method for PET imaging device, and computer-readable storage medium ) 是由 马聪 王武斌 李兴 于 2020-12-09 设计创作，主要内容包括：本发明提供了一种PET成像设备的堆积信号恢复方法、PET成像设备及计算机可读存储介质,恢复方法包括以下步骤：基于非堆积信号建立能量预测查找表及参考信号查找表,并存储入一个处理单元,将每一处理单元串接形成处理单元组；输入实时信号至第一处理单元,检测实时信号的第一峰值,匹配具有与第一峰值相同峰值的参考信号；监测实时信号于第一峰值后是否单调递减；当实时信号于第一峰值后未单调递减时,将参考信号与实时信号相减的差值信号输入至处理单元组的第二处理单元；第二处理单元及处理单元组内的第n处理单元反复求取差值信号直至差值信号于第一峰值后单调递减。采用上述技术方案后,可快速准确地恢复pile up信号。(The invention provides a method for recovering stacked signals of a PET imaging device, the PET imaging device and a computer readable storage medium, wherein the recovery method comprises the following steps: establishing an energy prediction lookup table and a reference signal lookup table based on the non-accumulation signals, storing the energy prediction lookup table and the reference signal lookup table into one processing unit, and connecting each processing unit in series to form a processing unit group; inputting a real-time signal to a first processing unit, detecting a first peak value of the real-time signal, and matching a reference signal having the same peak value as the first peak value; monitoring whether the real-time signal is monotonically decreased after the first peak value; when the real-time signal is not monotonically decreased after the first peak value, a difference signal obtained by subtracting the reference signal and the real-time signal is input to a second processing unit of the processing unit group; the second processing unit and the nth processing unit in the processing unit group repeatedly calculate the difference signal until the difference signal is monotonically decreased after the first peak value. After the technical scheme is adopted, the pile up signal can be quickly and accurately recovered.)

1. A pile-up signal recovery method of a PET imaging apparatus, comprising the steps of:

establishing an energy prediction lookup table and a reference signal lookup table based on the non-accumulation signal;

storing the energy prediction lookup table and the reference signal lookup table into at least one processing unit, and connecting each processing unit in series to form a processing unit group;

inputting a real-time signal of a PET imaging device to a first processing unit in the processing unit group, detecting a first peak value of the real-time signal, and traversing the first peak value in the reference signal lookup table to match a reference signal with the same peak value as the first peak value;

monitoring whether the real-time signal is monotonically decreased after the first peak value;

when the real-time signal is monotonically decreased after the first peak value, integrating the real-time signal by a first integration time to obtain an energy integral value of the real-time signal;

when the real-time signal is not monotonically decreased after the first peak value, integrating the real-time signal by using a second integration time, and traversing a leading edge integral energy value of an energy integral value of the real-time signal in the energy prediction lookup table to match a complete integral energy predicted value until the real-time signal is monotonically decreased after the first peak value;

subtracting the real-time signal from the reference signal to obtain a difference signal, and inputting the difference signal to a second processing unit of the processing unit group;

the second processing unit and the nth processing unit in the processing unit group repeatedly calculate the difference signal until the difference signal is monotonically decreased after the first peak value.

2. The pile-up signal recovery method of claim 1,

the steps of building an energy prediction look-up table and a reference signal look-up table based on the non-pile-up signal include:

collecting a non-accumulation signal, and integrating a leading edge waveform and a complete waveform of the non-accumulation signal to obtain a leading edge energy integral value and a complete energy integral value;

carrying out smoothing processing and interpolation processing on the leading edge energy integral value and the complete energy integral value to obtain a continuous corresponding relation of the leading edge energy integral value and the complete energy integral value;

and storing the continuous corresponding relation in an FPGA chip to form the energy prediction lookup table.

3. The pile-up signal recovery method of claim 2,

the step of building an energy prediction look-up table and a reference signal look-up table based on the non-pile-up signal further comprises:

collecting non-accumulation signals, and carrying out average processing on the amplitude values of the non-accumulation signals in a time domain to obtain a reference signal waveform;

and converting the amplitude of the reference signal waveform into a fixed value, and storing the fixed value to form a reference signal lookup table.

4. The pile-up signal recovery method of claim 1,

the second integration time is twice the first integration time.

5. The stacked signal recovery method of claim 1, further comprising the steps of:

a point source is close to an SiPM detector module to obtain A/D sampling data;

and comparing the A/D sampling data with the difference signal to judge the matching degree of the A/D sampling data and the difference signal.

6. A PET imaging device, comprising:

a database, wherein an energy prediction lookup table and a reference signal lookup table are established in the database based on non-accumulation signals;

the processing unit group is connected with the database and comprises at least one processing unit, and each processing unit stores an energy prediction lookup table and a reference signal lookup table;

a first processing unit in the processing unit group receives a real-time signal, detects a first peak value of the real-time signal, and traverses the first peak value in the reference signal lookup table to match a reference signal with the same peak value as the first peak value;

the first processing unit also monitors whether the real-time signal is monotonically decreased after the first peak value;

when the real-time signal is monotonically decreased after the first peak value, the first processing unit integrates the real-time signal with a first integration time to obtain an energy integration value of the real-time signal;

when the real-time signal is not monotonically decreased after the first peak value, the first processing unit integrates the real-time signal with a second integration time, and traverses a leading edge integral energy value of an energy integral value of the real-time signal in the energy prediction lookup table to match a complete integral energy predicted value until the real-time signal is monotonically decreased after the first peak value; the first processing unit subtracts the reference signal from the real-time signal to obtain a difference signal, and inputs the difference signal to a second processing unit of the processing unit group;

the second processing unit and the nth processing unit in the processing unit group repeatedly calculate the difference signal until the difference signal is monotonically decreased after the first peak value.

7. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of any of claims 1-5.

Technical Field

The present invention relates to the field of medical devices, and in particular, to a method for recovering a stacking signal of a PET imaging device, and a computer-readable storage medium.

Background

Positron Emission Tomography (PET) is a device that converts gamma rays emitted from a radioactive source into visible light using a crystal (such as BGO or Lyso), and then converts the visible light into analog electrical signals using a photoelectric conversion device (SiPM or PMT). The front-end circuit measures the energy and time of the analog electric signal with high precision, and then sends the measurement result to a back-end Data acquisition system (DAQ) for conformity judgment and selection. And finally, reconstructing a radiation source image by utilizing the time difference of a plurality of events of the effective signals on the coincidence line.

PET systems are mostly required to work with the more mobile radiation source. It is important to ensure that the detector will lose as little data as possible at high count rates. The signal pile-up phenomenon (pile up) is one of the key factors that the detector system needs to consider in high count rate situations. The pilup signal refers to the phenomenon that multiple gamma rays close in time hit a detector, producing multiple times the energy of normal gamma rays. Typical electronic system energy measurement circuits integrate a signal over a time window based on analog-to-digital conversion (a/D conversion). Therefore, for a temporally variable pile up signal, the integrated energy will deviate, resulting in a reduced effective count rate and reduced energy resolution of the system.

Therefore, a novel scheme for recovering the energy information of the pile up signal is needed, the pile up signal can be recovered more accurately, and the energy spectrum quality of the pile up signal can be improved.

Disclosure of Invention

In order to overcome the above technical defects, an object of the present invention is to provide a method for recovering a pile-up signal of a PET imaging device, a PET imaging device and a computer readable storage medium, which can rapidly and accurately recover a pile up signal.

The invention discloses a method for recovering stacked signals of PET imaging equipment, which comprises the following steps:

establishing an energy prediction lookup table and a reference signal lookup table based on the non-accumulation signal;

storing the energy prediction lookup table and the reference signal lookup table into at least one processing unit, and connecting each processing unit in series to form a processing unit group;

inputting a real-time signal of the PET imaging equipment to a first processing unit in a processing unit group, detecting a first peak value of the real-time signal, and traversing the first peak value in a reference signal lookup table to match a reference signal with the same peak value as the first peak value;

monitoring whether the real-time signal is monotonically decreased after the first peak value;

when the real-time signal is monotonically decreased after the first peak value, integrating the real-time signal by the first integration time to obtain an energy integral value of the real-time signal;

when the real-time signal is not monotonically decreased after the first peak value, integrating the real-time signal by using a second integration time, and traversing a leading edge integral energy value of an energy integral value of the real-time signal in an energy prediction lookup table to match a complete integral energy predicted value until the real-time signal is monotonically decreased after the first peak value;

subtracting the real-time signal from the reference signal to obtain a difference signal, and inputting the difference signal to a second processing unit of the processing unit group;

the second processing unit and the nth processing unit in the processing unit group repeatedly calculate the difference signal until the difference signal is monotonically decreased after the first peak value.

Preferably, the step of building the energy prediction lookup table and the reference signal lookup table based on the non-stacked signal comprises:

collecting a non-accumulation signal, and integrating a leading edge waveform and a complete waveform of the non-accumulation signal to obtain a leading edge energy integral value and a complete energy integral value;

carrying out smoothing processing and interpolation processing on the leading edge energy integral value and the complete energy integral value to obtain a continuous corresponding relation of the leading edge energy integral value and the complete energy integral value;

and storing the continuous corresponding relation in an FPGA chip to form an energy prediction lookup table.

Preferably, the step of building the energy prediction lookup table and the reference signal lookup table based on the non-stacked signal further comprises:

collecting non-accumulation signals, and carrying out average processing on the amplitude values of the non-accumulation signals in a time domain to obtain a reference signal waveform;

and converting the amplitude of the reference signal waveform into a fixed value, and storing the fixed value to form a reference signal lookup table.

Preferably, the second integration time is twice the first integration time.

Preferably, the method further comprises the following steps:

a point source is close to an SiPM detector module to obtain A/D sampling data;

and comparing the A/D sampling data with the difference signal to judge the matching degree of the A/D sampling data and the difference signal.

The invention also discloses a PET imaging device, comprising:

a database, wherein an energy prediction lookup table and a reference signal lookup table are established in the database based on the non-accumulation signals;

the processing unit group is connected with the database and comprises at least one processing unit, and each processing unit stores an energy prediction lookup table and a reference signal lookup table;

a first processing unit in the processing unit group receives the real-time signal, detects a first peak value of the real-time signal, and traverses the first peak value in a reference signal lookup table to match a reference signal with the same peak value as the first peak value;

the first processing unit also monitors whether the real-time signal is monotonically decreased after the first peak value;

when the real-time signal is monotonically decreased after the first peak value, the first processing unit integrates the real-time signal by a first integration time to obtain an energy integral value of the real-time signal;

when the real-time signal is not monotonically decreased after the first peak value, the first processing unit integrates the real-time signal by a second integration time, and traverses a leading edge integral energy value of an energy integral value of the real-time signal in an energy prediction lookup table to match a complete integral energy predicted value until the real-time signal is monotonically decreased after the first peak value; the first processing unit subtracts the reference signal and the real-time signal to obtain a difference signal, and inputs the difference signal to a second processing unit of the processing unit group;

the second processing unit and the nth processing unit in the processing unit group repeatedly calculate the difference signal until the difference signal is monotonically decreased after the first peak value.

The invention further discloses a computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of any of the above.

After the technical scheme is adopted, compared with the prior art, the method has the following beneficial effects:

1. the energy of the first piled-up signal can be quickly deduced based on a lookup table established by the integral value of the leading edge of the signal and the total energy of the signal;

2. based on a hierarchical recovery mechanism, non-stacked signals and energy can be accurately recovered.

Drawings

FIG. 1 is a flow chart of a method for pile-up signal recovery in a PET imaging device in accordance with a preferred embodiment of the invention;

FIG. 2 is a logic diagram of a method for pile-up signal recovery for a PET imaging device in accordance with a preferred embodiment of the invention;

FIG. 3 is a schematic diagram of the relationship between the value of the leading edge integrated energy and the value of the full integrated energy in accordance with a preferred embodiment of the present invention;

FIG. 4 is a waveform of a reference signal in accordance with a preferred embodiment of the present invention;

FIG. 5 is a diagram illustrating a waveform recovery result of a pile up signal according to a preferred embodiment of the present invention;

FIG. 6a is a schematic energy spectrum of a normal non-stacked signal in accordance with a preferred embodiment of the present invention;

FIG. 6b is a schematic energy spectrum of a fully integrated stacked signal in accordance with a preferred embodiment of the present invention;

FIG. 6c is a schematic energy spectrum of the first signal of the pile up signal after recovery processing according to a preferred embodiment of the present invention;

FIG. 6d is a schematic energy spectrum of the second signal of the pile up signal after recovery processing according to a preferred embodiment of the present invention.

Detailed Description

The advantages of the invention are further illustrated in the following description of specific embodiments in conjunction with the accompanying drawings.

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the exemplary embodiments below are not intended to represent all implementations consistent with the present disclosure. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present disclosure, as detailed in the appended claims.

The terminology used in the present disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used in this disclosure and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present disclosure. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.

In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.

In the description of the present invention, unless otherwise specified and limited, it is to be noted that the terms "mounted," "connected," and "connected" are to be interpreted broadly, and may be, for example, a mechanical connection or an electrical connection, a communication between two elements, a direct connection, or an indirect connection via an intermediate medium, and specific meanings of the terms may be understood by those skilled in the art according to specific situations.

In the following description, suffixes such as "module", "component", or "unit" used to denote elements are used only for facilitating the explanation of the present invention, and have no specific meaning in themselves. Thus, "module" and "component" may be used in a mixture.

Referring to fig. 1 and 2, a flow chart of a method for pile-up signal recovery of a PET imaging device according to a preferred embodiment of the invention is shown, in which the method for pile-up signal recovery comprises the following steps:

s100: establishing an energy prediction lookup table and a reference signal lookup table based on the non-accumulation signal;

and acquiring a large number of non-accumulation signals in the early stage, and establishing an energy prediction lookup table and a reference signal lookup table according to the energy and the waveform of the correct signal. That is, the energy prediction lookup table represents the energy in the time domain that should be represented in the normal signal (as shown in fig. 6 a), and the waveform pattern in the time domain that should be represented in the normal signal according to the statistics of a large number of samples, so as to serve as the reference object of the energy and the waveform.

S200: storing the energy prediction lookup table and the reference signal lookup table into at least one processing unit, and connecting each processing unit in series to form a processing unit group;

the PET imaging device or the processing unit group is connected with the PET imaging device in a communication mode and is formed by connecting at least one processing unit in series, namely, signals processed by the processing unit at the front stage are sent to the processing unit at the lower stage for continuous processing. Each processing unit stores the energy prediction lookup table and the reference signal lookup table, that is, each processing unit refers to the processing of the signal and processes the signal based on the energy prediction lookup table and the reference signal lookup table.

S300: inputting a real-time signal of the PET imaging equipment to a first processing unit in a processing unit group, detecting a first peak value of the real-time signal, and traversing the first peak value in a reference signal lookup table to match a reference signal with the same peak value as the first peak value;

the real-time signal of the PET imaging device is sent to a first processing unit in the processing unit group, that is, a first-stage processing unit of the processing unit group, and after receiving the real-time signal, the first processing unit detects a first peak value of the real-time signal, that is, a first peak value from front to back in a time domain, as a first peak value. After obtaining the first peak, the first processing unit traverses the first peak in the reference signal look-up table, and first matches a reference signal having the same peak as the first peak in the reference signal look-up table, so that the reference signal indicates that the real-time signal may substantially match one of the previous large number of signal samples under the condition that the first peak is the same, that is, according to the storage of the large number of samples, the subsequent waveform and energy of the real-time signal may be predicted.

S400: monitoring whether the real-time signal is monotonically decreased after the first peak value;

the above prediction should be understood as a prediction of non-stacked signal samples. The main reason is that, in general, for a normal non-stacked signal, the real-time signal should have only one peak, whereas under a stacked signal, multiple peak-to-peak values will occur. Therefore, after detecting the first peak value, the first processing unit will further process the real-time signal, that is, determine whether the real-time signal is in a monotonically decreasing state after the first peak value, and no peak value appears anymore.

Referring to fig. 3 and 4, the waveforms of the normal reference signals and the corresponding relationship between the leading edge integrated energy value and the full integrated energy value are shown, and the non-stacked signals should be matched with the waveforms of the normal reference signals as the reference objects.

S500: when the real-time signal is monotonically decreased after the first peak value, integrating the real-time signal by the first integration time to obtain an energy integral value of the real-time signal;

and when the judgment result of the first processing unit on the real-time signal is that the real-time signal is monotonically decreased after the first peak value, namely the peak value does not appear any more, the real-time signal is basically a non-accumulation signal, and the real-time signal is integrated within the first integration time, so that a correct complete energy integral value of the real-time signal is obtained.

S500': when the real-time signal is not monotonically decreased after the first peak value, integrating the real-time signal by using a second integration time, and traversing a leading edge integral energy value of an energy integral value of the real-time signal in an energy prediction lookup table to match a complete integral energy predicted value until the real-time signal is monotonically decreased after the first peak value;

when the real-time signal does not monotonically decrease after the first peak, i.e. one or more peaks again appear, indicating that a pile-up phenomenon occurs in the real-time signal, for this reason, the real-time signal will be integrated within the second integration time, and the integrated energy of the leading edge cut off to the first peak will be used to traverse the energy prediction look-up table (i.e. the influence of the subsequent peak on the energy is not considered for the moment). For the leading edge energy value, the leading edge energy value is traversed in the energy prediction lookup table like a complete energy integral value, and a complete integral energy prediction value (different from the complete integral energy value of the actual accumulation phenomenon) which the real-time signal should have if no accumulation phenomenon subsequently occurs is matched. The above steps are continuously executed when each peak value appears, that is, the corresponding peak value when each accumulation phenomenon occurs has the nth leading edge energy value, until the back side of the peak value is monotonically decreased after the last accumulation signal appears.

It will be appreciated that the above described constant deduction of the leading edge integrated energy prediction value will be performed in the primary processing unit each time.

S600: subtracting the real-time signal from the reference signal to obtain a difference signal, and inputting the difference signal to a second processing unit of the processing unit group;

and then, in the processing unit, subtracting the real-time signal from the reference signal to obtain a difference signal, namely a signal in which only the subsequent stacking signal is left after the real-time signal is the first peak value is removed, and inputting the difference signal into a value processing unit group to be used as a second processing unit of the lower stage of the first processing unit for continuous processing.

S700: the second processing unit and the nth processing unit in the processing unit group repeatedly calculate the difference signal until the difference signal is monotonically decreased after the first peak value.

The second processing unit and the nth processing unit in the processing unit group repeatedly obtain the difference signal, namely each stage of processing unit processes the once accumulation phenomenon, and the front edge energy predicted value is calculated and then removed until the difference signal is monotonically decreased after the first peak value.

Referring to fig. 5, by splitting the stacking phenomenon into a plurality of stacking phenomena and processing the stacking phenomena in a corresponding number of processing units, the stacking signals can be removed and restored to normal non-stacking signals, and the total energy of the stacking signals can be recovered.

Referring to fig. 6a to 6d, comparing the normal signal, the pile up spectrum without recovery processing, and the two pile up signal spectra before and after recovery processing, it can be seen that in this embodiment, the shape of the spectrum of the pile up is closer to the spectrum of the normal signal, that is, the purpose of recovering the energy of multiple pile up signals is achieved.

In a preferred embodiment, step S100 includes:

s110: collecting non-accumulation signals, and integrating the leading edge waveform and the complete waveform of the non-accumulation signals to obtain a leading edge energy integral value E_riseAnd integral value of complete energy E_sum；

S120: performing smoothing processing and interpolation processing on the leading edge energy integral value and the complete energy integral value, for example, obtaining a continuous corresponding relation of the leading edge energy integral value and the complete energy integral value by using an application program (such as Matlab) under an online environment;

s130: the successive correspondences are stored in an FPGA chip to form the energy prediction look-up table LUT1, which in this embodiment takes 10 bits for energy information, thus creating an energy prediction look-up table LUT1 with addresses from 0-1023.

Further, step S100 further includes:

s140: collecting non-accumulation signals, and carrying out average processing on the amplitude values of the non-accumulation signals in a time domain to obtain a reference signal waveform conforming to the characteristics of the Sipm signals;

s150: the amplitude of the reference signal waveform is converted to a fixed value and the fixed value is stored to form the reference signal look-up table LUT 2. The number of addresses in the lookup table is the same as the length of one integration (20 in the present invention). From the peak of the first signal, the waveform of the first signal can be deduced.

In the above embodiment, the detection of whether the time domain is the first peak value is mainly realized by monitoring the signal value in real time through peak detection and reference signal generation. When the first peak value appears, namely the peak value of the first signal is judged, then the multiplier is used for carrying out gain compensation processing on the reference signal lookup table, and a reference signal with the peak value identical to that of the first signal is output.

In a preferred embodiment, the second integration time is twice the first integration time, i.e. if the first integration time is T_int(400 ns in one embodiment of the present invention, mainly because the A/D sampling period is 20ns, the integration length is 20), the second integration time is 2T_int。

Further, the pile-up signal recovery method further includes the steps of:

s800: a point source. E.g., a Na22 point source, proximate to an SiPM detector module to obtain a/D sample data;

s900: and comparing the A/D sampling data with the difference signal to judge the matching degree of the A/D sampling data and the difference signal.

By adopting the gradual and gradual reduction recovery logic, the energy is predicted by using the front edge of the previous signal, the subsequent pile up signal is recovered by using a data subtraction method, and finally, the actual SiPM detector and the radiation source are used for preliminary test. Tests show that the scheme can accurately recover the pile up signal and can improve the energy spectrum quality of the pile up signal.

In another aspect, the present invention discloses a PET imaging apparatus comprising: a database, wherein an energy prediction lookup table and a reference signal lookup table are established in the database based on the non-accumulation signals; the processing unit group is connected with the database and comprises at least one processing unit, and each processing unit stores an energy prediction lookup table and a reference signal lookup table; a first processing unit in the processing unit group receives the real-time signal, detects a first peak value of the real-time signal, and traverses the first peak value in a reference signal lookup table to match a reference signal with the same peak value as the first peak value; the first processing unit also monitors whether the real-time signal is monotonically decreased after the first peak value; when the real-time signal is monotonically decreased after the first peak value, the first processing unit integrates the real-time signal by a first integration time to obtain an energy integral value of the real-time signal; when the real-time signal is not monotonically decreased after the first peak value, the first processing unit integrates the real-time signal by a second integration time, and traverses a leading edge integral energy value of an energy integral value of the real-time signal in an energy prediction lookup table to match a complete integral energy predicted value until the real-time signal is monotonically decreased after the first peak value; the first processing unit subtracts the reference signal and the real-time signal to obtain a difference signal, and inputs the difference signal to a second processing unit of the processing unit group; the second processing unit and the nth processing unit in the processing unit group repeatedly calculate the difference signal until the difference signal is monotonically decreased after the first peak value.

In yet another aspect, the invention discloses a computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps as described above.

It should be noted that the embodiments of the present invention have been described in terms of preferred embodiments, and not by way of limitation, and that those skilled in the art can make modifications and variations of the embodiments described above without departing from the spirit of the invention.