阅读说明：本技术 一种用于正电子发射成像的位置解码方法及系统 (Position decoding method and system for positron emission imaging ) 是由 许剑锋 解强强 张熙 于洪森 杜菁 谢思维 彭旗宇 于 2020-12-18 设计创作，主要内容包括：本发明公开了一种正电子发射成像的位置解码方法及系统,属于医疗影像领域。方法包括利用正电子发射产生的可见光得到多个能量阵列图；判断能量阵列图中是否发生康普顿事件,若是,剔除该能量阵列图,若否,保留该能量阵列图；找到过滤掉康普顿事件后的能量阵列图的峰值,以峰值为中心划分预设大小的局部区域,局部区域外的能量设置为零；在局部区域内利用重心解码算法定位正电子实际发生反应的位置。本发明提供的用于正电子发射成像的位置解码方法通过寻找康普顿事件,有效地过滤掉大量的康普顿散射事件,从而获得有效事件,防止康普顿散射事件影响解码图的效果。同时,局部区域的划分,有效地过滤掉大量环境噪声,使得解码图更为清晰。(The invention discloses a position decoding method and system for positron emission imaging, and belongs to the field of medical images. The method comprises the steps of obtaining a plurality of energy array maps by using visible light generated by positron emission; judging whether a Compton event occurs in the energy array diagram, if so, rejecting the energy array diagram, and if not, retaining the energy array diagram; finding a peak value of the energy array diagram after the Compton event is filtered out, dividing a local area with a preset size by taking the peak value as a center, and setting the energy outside the local area as zero; and (3) positioning the position where the positron actually reacts in the local area by using a gravity center decoding algorithm. According to the position decoding method for positron emission imaging, provided by the invention, a large number of Compton scattering events are effectively filtered out by searching for the Compton events, so that effective events are obtained, and the effect that the Compton scattering events influence a decoding graph is prevented. Meanwhile, a large amount of environmental noise is effectively filtered by dividing local areas, so that a decoded picture is clearer.)

1. A position decoding method for positron emission imaging, comprising the steps of:

s1, obtaining a plurality of energy array graphs by using visible light emitted by positrons;

s2, judging whether a Compton event occurs in the energy array diagram, if so, rejecting the energy array diagram, and if not, reserving the energy array diagram;

s3, finding a peak value of the energy array graph with the filtered Compton event, dividing a local area with a preset size by taking the peak value as a center, and setting the energy outside the local area to be zero;

and S4, positioning the position where the positron actually reacts in the local area by using a gravity center decoding algorithm.

2. The position decoding method of claim 1, wherein the energy array chart characterizes energy of visible light.

3. The position decoding method of claim 1, wherein there are two peaks in the energy array plot when a compton event occurs.

4. The position decoding method of claim 1, wherein the local region is smaller than a size of the energy array map.

5. The position decoding method of claim 4, wherein outside the local area is a dark event generated by ambient light.

6. A position decoding system for positron emission imaging, comprising: a computer-readable storage medium and a processor;

the computer-readable storage medium is used for storing executable instructions;

the processor is configured to read executable instructions stored in the computer-readable storage medium and execute the position decoding method for positron emission tomography according to any one of claims 1 to 5.

Technical Field

The invention belongs to the field of medical images, and particularly relates to a position decoding method and system for positron emission imaging.

Background

PET (Positron Emission Tomography) performs tomographic imaging by detecting gamma rays generated after decay of a radionuclide. The radionuclides used in PET decay to produce positrons. Positrons are antiparticles of electrons, and when positrons generated after radioactive nuclides injected into a living body decay pass through tissues of the living body, annihilation is carried out on the positrons and negative electrons in the tissues within a short distance (about 0.5mm, different positive electron nuclides have different positron annihilation distances), all masses are converted into energy to be released, and gamma photon pairs with energy approximate to 180 degrees and up to 511keV are generated. The pair of gamma photons is detected along the emission direction, and the line integral value of the radionuclide distribution decaying in the emission direction is obtained, so that the tomographic image reconstruction is performed.

PET is the only new imaging technology that can show biomolecular metabolism, receptor and nerve mediator activity in vivo, and has been widely used in diagnosis and differential diagnosis of various diseases, judgment of disease conditions, evaluation of therapeutic effects, research of organ functions, development of new drugs, and the like.

The spatial resolution is one of the important performances in the PET system, and is an important index of the imaging quality of the system, and the spatial resolution depends on the quality of the decoding image in the previous period, so the quality of the decoding image needs to be improved, and the spatial resolution needs to be improved.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a position decoding method and a position decoding system for positron emission tomography, and aims to solve the problem of low decoding quality of the existing position decoding method.

To achieve the above object, an aspect of the present invention provides a position decoding method for positron emission tomography, comprising the steps of:

s1, obtaining a plurality of energy array graphs by utilizing visible light obtained by reaction of gamma photons generated by positron emission in a scintillation crystal;

s2, judging whether a Compton event occurs in the energy array diagram, if so, rejecting the energy array diagram, and if not, reserving the energy array diagram;

s3, finding a peak value of the energy array graph with the filtered Compton event, dividing a local area with a preset size by taking the peak value as a center, and setting the energy outside the local area to be zero;

and S4, positioning the position where the positron actually reacts in the local area by using a gravity center decoding algorithm.

Further, the energy array graph characterizes the energy of visible light.

Further, according to the characteristics of Compton scattering, suspicious events with Compton scattering are found out, when the Compton events occur, two peak values exist in the energy array diagram, and then the Compton scattering is judged to occur and eliminated.

Further, the local area is smaller than the size of the energy array map, and dividing the local area is used for reducing the influence of Sipm (Silicon photomultiplier) noise outside the area.

Further, outside the local area is a dark event generated by ambient light.

In another aspect, the present invention provides a position decoding system for positron emission tomography, comprising: a computer-readable storage medium and a processor;

the computer-readable storage medium is used for storing executable instructions;

the processor is used for reading executable instructions stored in the computer readable storage medium and executing the position decoding method for positron emission tomography. .

Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. according to the position decoding method for positron emission imaging, provided by the invention, a large number of Compton scattering events are effectively filtered out by searching for the Compton events, so that effective events are obtained, and the effect that the Compton scattering events influence a decoding graph is prevented.

2. The position decoding method for positron emission imaging provided by the invention effectively filters a large amount of environmental noise by dividing local areas, so that a decoding image is clearer.

Drawings

FIG. 1 is a schematic illustration of a reaction of positrons, without Compton events, in a scintillation crystal to produce visible light, as provided by an embodiment of the present invention;

FIG. 2 is a schematic diagram of a scintillation crystal in which a positron having a Compton event has reacted to produce visible light, according to an embodiment of the present invention;

FIG. 3 is a diagram of a (local) energy array with Compton events occurring, as provided by an embodiment of the present invention;

FIG. 4 is a diagram of an energy array provided by an embodiment of the present invention;

figure 5 is a final decoded picture of positron emission provided by an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a position decoding method for positron emission imaging, which comprises the following steps:

s1, obtaining a plurality of energy array graphs by using visible light emitted by positrons;

s2, judging whether a Compton event occurs in the energy array diagram, if so, rejecting the energy array diagram, and if not, reserving the energy array diagram;

s3, finding a peak value of the energy array graph with the filtered Compton event, dividing a local area with a preset size by taking the peak value as a center, and setting the energy outside the local area to be zero;

and S4, positioning the position where the positron actually reacts in the local area by using a gravity center decoding algorithm.

FIG. 1 is a schematic diagram illustrating the reaction of positrons, where no Compton event has occurred, in a scintillation crystal having a ribbon in which gamma photons from a radiation source are captured to produce visible light, according to the present invention; the crystal is separated by a barium sulfate interlayer, the barium sulfate has certain light transmittance, visible light can penetrate a small amount, and the Sipm is used for receiving the visible light emitted from the crystal, converting the visible light into an electric signal and transmitting the electric signal to a rear-end electronic circuit system. When there is no Compton event, there is only one reaction point, and the energy value obtained only at some Sipm adjacent to the crystal bar is high, and due to the effect of the barium sulfate interlayer, the attenuation of visible light is increased when the visible light diffuses from the reaction point to the periphery, so that a peak is formed in the energy array diagram, and the event is an effective event.

FIG. 2 is a schematic diagram illustrating the reaction of a positron having a Compton event in a scintillation crystal to produce visible light, a bar of the scintillation crystal capturing gamma photons from a radiation source, the gamma photons reacting within the bar to form visible light, in accordance with the present invention; the crystal is separated by a barium sulfate interlayer, the barium sulfate has certain light transmittance, visible light can penetrate a small amount, and the Sipm is used for receiving the visible light emitted from the crystal, converting the visible light into an electric signal and transmitting the electric signal to a rear-end electronic circuit system. When the event generates Compton scattering, and when the reaction occurs in the original crystal bar, the gamma photon is partially scattered into other crystal bars so as to generate visible light in other crystal bars, the crystal bar of the original reaction point and the crystal bar of the new reaction point can almost simultaneously generate respective visible light, and here, for convenience, only one Compton scattering is considered, and when the Compton scattering is performed for multiple times, the energy value can be attenuated, and the influence on the decoding effect can be ignored. After a compton event occurs, two peaks are formed in the obtained energy array diagram, and the event is the compton event, which affects the effect of a decoding diagram and causes the reduction of resolution.

Fig. 3 shows a (local) energy array diagram of a compton event according to the invention, determining whether the event is a compton event, i.e. detecting whether two peaks are formed by the event. Specifically, energy data of all channels of the energy array (36 channels are taken in the present embodiment) is acquired.

First, find the maximum energy value of the event, as shown in fig. 3, find the position with energy value of 200;

and secondly, setting the energy of the channel with the energy value of 200 and the energy of other four channels which form a cross up, down, left and right as 0 together, and finding out the maximum energy value after setting the energy value to 0.

And thirdly, judging whether the energy value is a new peak value, recovering the energy of other four channels which form the cross around the channel with the energy value of 200 to be the original energy value, and comparing the energy values of the four channels with the newly found maximum energy value.

Fourthly, if the energy value is larger than any one of the energy values of the other four channels, the energy value is a new peak value, and a Compton event happens; if not, it indicates that no Compton event has occurred.

By screening all events, events without Compton scattering can be obtained, the events can be used for subsequent decoding, and the events with Compton scattering need to be eliminated.

Fig. 4 shows a diagram of an energy array provided in accordance with an embodiment of the invention. After the reaction and the Compton event are rejected, an energy peak is formed, as shown in the figure, at the center within the dashed box, with an energy value of 100; when visible light formed in an actually reacted crystal bar diffuses towards the periphery, the visible light is attenuated along with the diffusion due to the effect of the barium sulfate interlayer, and when the visible light is far away, the diffused visible light is influenced by environmental noise and is submerged in the environmental noise. Therefore, the present invention uses the surrounding region of the maximum energy peak for center of gravity decoding, and the energy values outside the region are not considered. Specifically, the method comprises the following steps:

step one, finding out the position of the energy peak value of the event, as shown in fig. 4, the energy peak value is 100;

and secondly, taking Sipm with the energy peak value of 100 as a center, drawing a local area outwards as shown by a broken line frame in fig. 4, wherein the energy value in the area is reserved, and the energy value outside the area is set to be 0. When the energy peak is at the edge, a boundary may be expanded outward to the whole area, where the energy value of the boundary is 0, and then the above operation is performed, and finally the global restoration is performed.

And thirdly, solving the position of the event by using a gravity center algorithm.

Finally, a final decoding diagram of the positron emission provided by the embodiment of the invention shown in fig. 5 is obtained.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.