WO2018049962A1

WO2018049962A1 - Simplified model of scintillation pulse, and reconstruction and energy acquisition method therefor

Info

Publication number: WO2018049962A1
Application number: PCT/CN2017/097761
Authority: WO
Inventors: 刘世豪
Original assignee: 湖北锐世数字医学影像科技有限公司
Priority date: 2016-09-14
Filing date: 2017-08-17
Publication date: 2018-03-22
Also published as: CN106443760A; CN106443760B

Abstract

Disclosed is a simplified model construction method for a scintillation pulse, comprising the following steps: in the process of using an original scintillation pulse model (I) to reconstruct a scintillation pulse signal obtained through practical sampling, for scintillation pulses of different energies, defining a practical start moment t₀ of a scintillation pulse, a pulse rise time related parameter b and a pulse fall time related parameter d not changing and only a pulse amplitude a changing; and during the reconstruction of the scintillation pulse, regarding a moment of a pulse sampling value as a moment 0, and then constructing a simplified model of the scintillation pulse to be (II), wherein t'₀, b₀and d₀ are respectively empirical values of t₀, b and d in the original scintillation pulse model. Also comprised are a scintillation pulse reconstruction method and a rapid energy information acquisition method, which can effectively reduce the complexity of the reconstruction of a scintillation pulse and accelerate the speed of the reconstruction of the scintillation pulse and that of the acquisition of energy information, and can also reduce the deterioration of a system energy resolution ratio as much as possible.

Description

Method for simplifying model, reconstruction and energy acquisition of scintillation pulse

Technical field

The invention belongs to the technical field of photoelectric detection, and relates to a model reconstruction and energy determination method for high-speed scintillation pulses.

Background technique

The traditional digital scintillation pulse energy calculation method calculates the scintillation pulse (establishing the original scintillation pulse model), and reconstructs the scintillation pulse by curve fitting to obtain its energy value by integration. According to the mathematical model of the scintillation pulse, when the scintillation pulse is reconstructed by the curve fitting method, it is necessary to fit 3 to 4 variations, which requires high computational complexity and long calculation time, as follows:

The actual sampled pulse signal is reconstructed by the following original scintillation pulse model:

Where t ₀ is the pulse start time and b and d are the parameters related to the pulse rise time and decay time. When reconstructing the pulsed sample signal, it is necessary to calculate four parameters a, t ₀ , b and d based on the acquired pulse sample values.

After the completion of the scintillation pulse reconstruction, the energy information is obtained by the following formula:

In the process of reconstructing and calculating the scintillation pulse using the above method, multiple complex operations such as power exponential and logarithm are involved, which requires high computational complexity and long calculation time. In the actual computer operation process, the computing resources are greatly consumed.

Summary of the invention

The object of the invention is to provide a simplified model of scintillation pulse and a fast acquisition method of energy information, which reduces the complexity of scintillation pulse reconstruction, accelerates scintillation pulse reconstruction and energy information acquisition speed, and minimizes deterioration of system energy resolution. .

To achieve the above object, the solution of the present invention is:

The invention discloses a method for establishing a scintillation pulse simplified model, comprising the following steps:

Raw scintillation pulse model

During the reconstruction process of the actual sampled scintillation pulse signal, the actual start time t _{0 of the} flicker pulse, the pulse rise time related parameter b and the pulse decay time related parameter d do not change for the scintillation pulse of different energy, only in the pulse The amplitude a changes, and when the scintillation pulse is reconstructed, the time of the pulse sample value is taken as 0 time, and the simplified model of the scintillation pulse is established as follows:

Where t' ₀ , b ₀ and d ₀ are the empirical values of t ₀ , b and d in the original scintillation pulse model, respectively.

Preferably, the predetermined empirical value t t _0, b and d _{_'0,} b _0, and d ₀ scintillation pulse via the original model, and determines a pulse amplitude value is obtained based on the actual value of the pulse sampling.

Further, the determining t _{_'0,} b _0, and d ₀ values comprising the steps of:

(I) obtaining raw pulse information y'(t)=f(t,v) by high speed sampling;

(II) Obtain the values of t _0i , b _i and d _i of the partial channels, taking the average values of t _0i , b _i and d _i as empirical values t′ ₀ , b ₀ and d ₀ , respectively, and the set of empirical values Applied to all channels, where i is the number of the detector channel;

Or the t 'comprising the steps of obtaining _0, b ₀ and the value of D _0:

(I') obtaining original pulse information y'(t)=f(t,v) by high speed sampling;

Each channel (II ') get the value of the plurality of sets of t _0i, b _i, and d _i, respectively, to obtain multiple sets t _0i, b _i, and d _i values in each channel are averaged, and as the The empirical values of the channels t' ₀ , b ₀ and d _{0 are} applied to the corresponding channels, where i is the number of the detector channel.

Further, the raw pulse information y'(t) = f(t, v) is obtained via high speed ADC sampling or MVT sampling modeling.

Preferably, the obtaining of the pulse amplitude a comprises the following steps:

make

And using the least squares method to fit the unknown parameter a, then:

Where (t _i , y _i ) is the actually obtained pulse sample value, and N is the actual number of samples.

The invention also discloses a scintillation pulse reconstruction method, comprising the following steps:

(a) Establish a simplified model of the scintillation pulse according to the aforementioned method:

(b) reconstructing the actually sampled pulse signal according to the scintillation pulse simplification model.

Preferably, in the step (a), the scintillation pulse is generated by the same detector.

The invention also discloses a method for quickly acquiring scintillation pulse energy information, comprising the following steps:

(1) A method for establishing a scintillation pulse simplified model according to the method of any one of claims 1 to 5:

(2) determining pulse energy information E according to the simplified model, then pulse energy information

The invention also discloses a fast energy information acquisition method for scintillation pulse MVT sampling data, comprising the following steps

(A) Sampling the scintillation pulse using the MVT method to obtain the pulsed MVT sample value

(B) Calculating energy information of the MVT sample value using the scintillation pulse energy information quick acquisition method according to claim 8.

Due to the adoption of the above scheme, the beneficial effects of the present invention are:

The present invention provides a simplified model of a scintillation pulse. The scintillation pulses of different energies change only in the pulse amplitude (a), and the three parameters t ₀ , b and d do not change, and the scintillation pulse is performed by using a high sampling rate. Sampling and offline reconstruction of the scintillation pulse to obtain multiple reconstruction parameters; using the above-mentioned scintillation pulse to simplify the model to actually reconstruct the scintillation pulse, only need to fit the pulse amplitude a, which greatly reduces the complexity of scintillation pulse reconstruction. The flashing pulse reconstruction speed can be effectively accelerated; at the same time, the energy information of the scintillation pulse is calculated according to the pulse amplitude a of each scintillation pulse, and the scintillation pulse waveform can be quickly reconstructed by using fewer scintillation pulse sampling points to obtain the energy information of the original pulse. The energy information of the fully digitized scintillation pulse can be extracted.

DRAWINGS

1 is a schematic flow chart of a method for establishing a scintillation pulse simplified model according to the present invention;

2 is a scintillation pulse sample and a post-reconstruction pulse obtained using a high sampling rate ADC;

3 is a waveform diagram of pulse reconstruction of MVT sample values using a simple model;

Figure 4 is an energy distribution diagram obtained by pulse reconstruction of MVT sample values using a simple model;

Figure 5 shows the energy resolution of different detectors;

Figure 6 is a graphical representation of the energy resolution obtained using the energy resolution obtained by high sampling rate ADC modeling and the fast energy information acquisition method using scintillation pulse MVT sampling data.

detailed description

The invention will be further described below in conjunction with the embodiments shown in the drawings.

First Embodiment: As shown in FIG. 1, the present invention discloses a method for establishing a scintillation pulse simplified model, comprising the following steps: using an original scintillation pulse model

During the reconstruction process of the actual sampled flicker pulse signal, the actual start time t _{0 of the} flicker pulse, the pulse rise time related parameter b and the pulse decay time related parameter d do not change for the scintillation pulse of different energy, only in the pulse The amplitude a changes, and when the scintillation pulse is used for reconstruction, the time of the pulse sample value is taken as 0 time, so that the actual start time t _{0 of the} flicker pulse will occur before time 0;

Original scintillation pulse model

Simplified to:

Wherein, the empirical values t0 ₀ , b ₀ and d _{0 of} t ₀ , b and d can be obtained in advance via the original scintillation pulse model, and the pulse amplitude a value is determined according to the actually obtained pulse sampling value; The prior conditions can be determined by multiple data acquisition and curve fitting for each acquisition channel, and the specific values of empirical values t' ₀ , b ₀ and d ₀ are determined according to the t ₀ , b and d values of the scintillation pulses of each acquisition channel. Value.

Specifically, the following methods are included

method one:

(I) Obtain the original pulse information by high-speed sampling y(t)=f(t,v)

The pulse is reconstructed by means of ADC high-speed sampling (ie by modeling the scintillation pulse (establishing the original scintillation pulse model) and obtaining the scintillation pulse using curve fitting), or by using the MVT sampling method to pulse Reconstruction, and determine the original pulse information y (t) = f (t, v), wherein the scintillation pulse sample obtained by the high-speed sampling method of the ADC and the reconstructed pulse are as shown in Fig. 2, the smooth curve is the original scintillation pulse, non-smooth The curve is the reconstructed scintillation pulse.

(II) obtaining the values of t _0,i , b _i and d _i of the partial channel, taking the average values of t _0,i , b _i and d _i as the empirical values t′ ₀ , b ₀ and d ₀ , respectively, and This set of experience values is applied to all channels i;

The pulse sample obtained by the ADC with high sampling rate is reconstructed according to the original scintillation pulse model or the pulse is reconstructed by the MVT sampling method. After the original pulse information y(t)=f(t,v) is determined, the original pulse is determined. Information y(t), arbitrarily select different detection channels i, and perform offline reconstruction of the scintillation pulses in the detection channel i according to the original scintillation pulse model, and obtain multiple sets of reconstruction parameters t _0,i , b _i and d _i , as much as possible The pulse energy pulse near the energy peak obtains an accurate value after reconstruction, and the pulse value of the pulse energy in a certain range near the energy peak is used to obtain the empirical values t' ₀ , b ₀ and d ₀ determined according to the following formula, and The empirical values t' ₀ , b ₀ and d _{0 are applied} as empirical values to all channels i

Method 2, on the basis of the first method, in order to further improve the accuracy, the specific values of the empirical values t′ ₀ , b ₀ and d ₀ can also be determined by the following methods.

(I') Obtain the original pulse information y'(t)=f(t,v) by high-speed sampling

As in Method 1, the pulse is first reconstructed by the ADC high-speed sampling method (ie, by modeling the scintillation pulse (establishing the original scintillation pulse model) and obtaining, and using the curve fitting method to reconstruct the scintillation pulse), or The pulse is reconstructed using the MVT sampling method, and the original pulse information y'(t) = f(t, v) is determined.

Each channel (II ') get the value of the plurality of sets of t _{_0i,} b _0i and d _0i, respectively, to obtain multiple sets t _{_0i,} b _0i d _0i and the average value is taken for each channel, and as the The empirical values of the channels t' ₀ , b ₀ and d _{0 are} applied to the corresponding channels.

After the pulse is reconstructed according to the original scintillation pulse model or the pulse is reconstructed by the MVT sampling method using the pulse sample value obtained at a high speed, each group of each detection channel i is obtained for each of the scintillation pulses in each detection channel i. _0i , b _i and d _i , in order to obtain the exact value of the pulse energy near the energy peak after reconstruction, in each detector channel i, using pulse energy to obtain the pulse reconstruction parameters within a certain range near the energy peak according to the following equation to determine the empirical value, and experience value t _{_'0,} b _0, and d _0, as applied to experience the corresponding detection in the channel i.

After determining the empirical values t′ ₀ , b ₀ and d ₀ of each detection channel i, it is also necessary to perform fitting according to the actually obtained pulse sampling values as the value of the unknown parameter a. In this embodiment,

And using the least squares method to fit the unknown parameter a, the following results are obtained:

Where (t _i , y _i ) is the actually obtained pulse sample value, and N is the actual number of samples. In the actual calculation of the a value, only a finite number of times (related to N) exponential operation is needed, which reduces the complexity of the scintillation pulse reconstruction algorithm.

Substituting the above empirical values t' ₀ , b ₀ and d ₀ and the pulse amplitude a value into the scintillation pulse simplified model

Just fine.

Second Embodiment: The present invention discloses a scintillation pulse reconstruction method, which includes the following steps:

(a) Establish a simplified model of the scintillation pulse: using the original scintillation pulse model

During the reconstruction process of the actual sampled scintillation pulse signal, the actual start time t _{0 of the} flicker pulse, the pulse rise time related parameter b and the pulse decay time related parameter d do not change for the scintillation pulse of different energy, only in the pulse The amplitude a changes, and when the scintillation pulse is used for reconstruction, the time of the pulse sample value is taken as 0 time, so that the actual start time t _{0 of the} flicker pulse will occur before time 0; then the original scintillation pulse model can be

Simplified to:

(b) reconstructing the actually sampled pulse signal according to the scintillation pulse simplification model. In this embodiment, the scintillation pulse is reconstructed using a curve fitting method.

As a preferred solution, in step (a), the scintillation pulses are generated by the same detector, that is, a simplified model is applied to the scintillation pulses generated by the same detector channel and reconstructed with higher accuracy.

In the scintillation pulse reconstruction method shown in the present invention, when the scintillation pulse is actually reconstructed, since the pulse signal obtained by the actual sampling is reconstructed by using a simplified model, only the pulse amplitude a needs to be fitted, and the flicker is greatly reduced. The pulse reconstruction complexity speeds up the reconstruction of the scintillation pulse.

In the third embodiment, the present invention discloses a method for quickly acquiring scintillation pulse energy information, which includes the following steps:

Simplified to:

Since the same pulse has a similar pulse waveform, when the scintillation crystal and the front-end circuit are determined, the rise time and decay time of the flicker pulse generated in different channels do not change much, and the rise time related parameter b and the decay time related parameter d can be considered. Similarly, the scintillation pulse energy is mainly determined by the pulse amplitude a. The empirical values t′ ₀ , b ₀ and d _{0 of} t ₀ , b and d may be obtained in advance via the original scintillation pulse model, and the pulse amplitude a value is determined according to the actually acquired pulse sample values;

In this embodiment, according to the a priori condition in step (1), multiple data acquisition and curve fitting can be performed for each acquisition channel, and the experience is determined according to the t ₀ , b, and d values of the scintillation pulses of each acquisition channel. The specific values of the values t' ₀ , b ₀ and d ₀ specifically include the following steps:

(I) Obtain the original pulse information y'(t)=f(t,v) by high-speed sampling

The pulse is reconstructed by means of ADC high-speed sampling (ie by modeling the scintillation pulse (establishing the original scintillation pulse model) and obtaining the scintillation pulse using curve fitting), or by using the MVT sampling method to pulse Reconstruct and determine the original pulse information y'(t) = f(t, v).

The pulse sample value obtained by the ADC with high sampling rate is reconstructed according to the original scintillation pulse model or the pulse is reconstructed by MVT sampling method. After the original pulse information y'(t)=f(t,v) is determined, the original is Pulse information y(t), arbitrarily select different detection channels i, and perform offline reconstruction of the scintillation pulse in the detection channel i according to the original scintillation pulse model, and obtain multiple sets of reconstruction parameters t _0,i , b _i and d _i as much as possible pulse energy values to obtain accurate reconstruction in the vicinity of the peak pulse energy, pulse energy pulse reconstruction parameters used in a nearby energy peak obtained for a range determined according to the following equation empirical value t _{_'0,} b _0, and d _0. And apply the empirical values t' ₀ , b ₀ and d ₀ as empirical values to all channels i

(3) After obtaining the empirical values t ₀ , b ₀ and d ₀ and the value of a, the pulse energy information can be obtained by the following calculation:

In this way, the previous exponential curve fitting can be simplified to straight line fitting, the computational complexity is greatly reduced, and the calculation time is greatly shortened.

Fourth Embodiment: In order to further improve the accuracy, on the basis of the third embodiment, the present invention also discloses a method for quickly parameterizing the scintillation pulse energy information, comprising the following steps:

Simplified to:

Since the same pulse has a similar pulse waveform, when the scintillation crystal and the front-end circuit are determined, the rise time and decay time of the flicker pulse generated in different channels do not change much, and the rise time related parameter b and the decay time related parameter d can be considered. Similarly, the scintillation pulse energy is mainly determined by the pulse amplitude a. Wherein, the empirical values t0 ₀ , b ₀ and d _{0 of} t ₀ , b and d can be obtained in advance via the original scintillation pulse model, and the pulse amplitude a value is determined according to the actually acquired pulse sample values;

According to the a priori condition in the step (1), the empirical value t' ₀ can be determined according to the t ₀ , b and d values of the scintillation pulses of each acquisition channel by performing multiple data acquisition and curve fitting on each acquisition channel. The specific values of b ₀ and d ₀ specifically include the following steps:

(I') Obtain the original pulse information y'(t)=f(t,v) by high-speed sampling

After the pulse is reconstructed according to the original scintillation pulse model or the pulse is reconstructed by the MVT sampling method using the pulse sample value obtained at a high speed, each group of each detection channel i is obtained for each of the scintillation pulses in each detection channel i. _0i , b _i and d _i , in order to obtain the exact value of the pulse energy near the energy peak after reconstruction, in each detector channel i, using pulse energy to obtain the pulse reconstruction parameters within a certain range near the energy peak experience and the experience value t _{_'0,} b _0, and d _0, as applied to experience the corresponding detection in the channel i.

After determining the empirical values t ₀ , b ₀ and d ₀ of each detection channel i, it is also necessary to obtain the value of the unknown parameter a according to the actually obtained pulse sample value. In this embodiment,

In a fifth embodiment, the present invention also discloses a fast energy information acquisition method for scintillation pulse MVT sampling data, (a) sampling the scintillation pulse using the MVT method to obtain a pulsed MVT sample value, and (b) sampling the samples. The value is reconstructed using a scintillation pulse simplified model and then utilized

The energy information of the pulse can be obtained.

In order to verify the reliability and accuracy of the simplified model shown in the present invention and the pulse reconstruction and energy determination method using the simplified model, the scintillation pulse reconstruction and energy calculation are combined with the simplified model and the MVT sampling method shown in the present invention. First, The MVT method is used to sample the pulse, and the pulsed MVT sample values are obtained. The sampled values are reconstructed using a scintillation pulse simplified model. The reconstructed pulse is shown in the smooth curve in Figure 3, and then used.

The energy information of the pulse can be obtained, as shown by the smooth curve in FIG.

Further, for a plurality of detectors, the energy distribution map and the energy peak resolution are obtained by the fast energy information acquisition method of the scintillation pulse MVT sampling data shown in the present invention, and are performed with the obtained standard values of the high-speed sampling. Comparing, the results are shown in Figure 5 and Figure 6. Figure 6 shows that the energy resolution (continuous spacing line) of each channel obtained using the fast method is better than the energy resolution of each channel obtained by sampling with high-speed ADC (intermittent spacing line). The results show that using the new fast energy acquisition method to calculate the sample values obtained by MVT, the energy resolution is improved.

The above description of the embodiments is intended to facilitate the understanding and use of the invention by those skilled in the art. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the general principles described herein can be applied to other embodiments without the inventive work. Therefore, the present invention is not limited to the embodiments described above, and those skilled in the art should be able to make modifications and changes within the scope of the invention without departing from the scope of the invention.

Claims

A method for establishing a scintillation pulse simplified model, comprising the steps of:

Raw scintillation pulse model
During the reconstruction process of the actual sampled scintillation pulse signal, the actual start time t 0 of the flicker pulse, the pulse rise time related parameter b and the pulse decay time related parameter d do not change for the scintillation pulse of different energy, only in the pulse The amplitude a changes, and when the scintillation pulse is reconstructed, the time of the pulse sample value is taken as 0 time, and the simplified model of the scintillation pulse is established as follows:

Where t' 0 , b 0 and d 0 are the empirical values of t 0 , b and d in the original scintillation pulse model, respectively.
The scintillation pulse simplified model establishment method according to claim 1, wherein: the predetermined model via the original scintillation pulse t 0, the experience value of b and d t '0, b 0, and d 0, and the actual acquired The pulse sample value determines the pulse amplitude a value.
The simplified model scintillation pulse or establishment method according to claim 12, wherein the determined '0, b 0, and d 0 t values comprises the steps of:

(I) obtaining raw pulse information y'(t)=f(t,v) by high speed sampling;

(II) Obtain the values of t 0i , b i and d i of the partial channels, taking the average values of t 0i , b i and d i as empirical values t′ 0 , b 0 and d 0 , respectively, and the set of empirical values Applied to all channels, where i is the number of the detector channel;

Or the t 'comprising the steps of obtaining 0, b 0 and the value of D 0:

(I') obtaining original pulse information y'(t)=f(t,v) by high speed sampling;

Each channel (II ') get the value of the plurality of sets of t 0i, b i, and d i, respectively, to obtain multiple sets t 0i, b i, and d i values in each channel are averaged, and as the The empirical values of the channels t' 0 , b 0 and d 0 are applied to the corresponding channels, where i is the number of the detector channel.
The scintillation pulse simplified model establishing method according to claim 3, characterized in that the original pulse information y'(t) = f(t, v) is obtained via high speed ADC sampling or MVT sampling modeling.
The method for establishing a scintillation pulse simplified model according to claim 1 or 2, wherein the obtaining of the pulse amplitude a comprises the following steps:

make
And using the least squares method to fit the unknown parameter a, then:

Where (t i , y i ) is the actually obtained pulse sample value, and N is the actual number of samples.
A scintillation pulse reconstruction method, comprising: the following steps:

(a) A method for establishing a scintillation pulse simplification model according to the method of any one of claims 1 to 5:

(b) reconstructing the actually sampled pulse signal according to the scintillation pulse simplification model.
The scintillation pulse reconstruction method according to claim 6, wherein in the step (a), the scintillation pulse is generated by the same detector.
A method for quickly acquiring scintillation pulse energy information, comprising: the following steps:

(1) A method for establishing a scintillation pulse simplified model according to the method of any one of claims 1 to 5:

(2) determining pulse energy information E according to the simplified model, then pulse energy information
A fast energy information acquisition method for scintillation pulse MVT sampling data, comprising: the following steps

(A) Sampling the scintillation pulse using the MVT method to obtain the pulsed MVT sample value

(B) Calculating energy information of the MVT sample value using the scintillation pulse energy information quick acquisition method according to claim 8.