Multi-photon time-of-flight MLEM application for the positronium imaging in J-PET

IF 1.2 Q3 Computer Science
R. Shopa, K. Dulski
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引用次数: 3

Abstract

We develop a positronium imaging method for the Jagiellonian PET (J-PET) scanners based on the time-of-flight maximum likelihood expectation maximisation (TOF MLEM). The system matrix elements are calculated on-the-fly for the coincidences comprising two annihilation and one de-excitation photons that originate from the ortho-positronium (o-Ps) decay. Using the Geant4 library, a Monte Carlo simulation was conducted for four cylindrical 22Na sources of β+ decay with diverse o-Ps mean lifetimes, placed symmetrically inside the two JPET prototypes. The estimated time differences between the annihilation and the positron emission were aggregated into histograms (one per voxel), updated by the weights of the activities reconstructed by TOF MLEM. The simulations were restricted to include only the o-Ps decays into back-to-back photons, allowing a linear fitting model to be employed for the estimation of the mean lifetime from each histogram built in the log scale. To suppress the noise, the exclusion of voxels with activity below 2% – 10% of the peak was studied. The estimated o-Ps mean lifetimes were consistent with the simulation and distributed quasi -uniformly at high MLEM iterations. The proposed positronium imaging technique can be further upgraded to include various correction factors, as well as be modified according to realistic o-Ps decay models.
多光子飞行时间MLEM在J-PET正电子成像中的应用
我们为Jagiellonian PET(J-PET)扫描仪开发了一种基于飞行时间最大似然期望最大化(TOF-MLEM)的正电子成像方法。系统矩阵元素是为包括两个湮灭和一个去激发光子的重合而动态计算的,这两个光子源自正正电子(o-Ps)衰变。使用Geant4库,对对称放置在两个JPET原型内部的四个具有不同o-Ps平均寿命的β+衰变的圆柱形22Na源进行了蒙特卡罗模拟。湮灭和正电子发射之间的估计时间差被聚集成直方图(每个体素一个),由TOF MLEM重建的活动的权重更新。模拟被限制为仅包括o-Ps衰变为背靠背光子,从而允许使用线性拟合模型根据对数尺度中构建的每个直方图来估计平均寿命。为了抑制噪声,研究了活动度低于峰值2%-10%的体素的排除。估计的o-Ps平均寿命与模拟结果一致,并且在高MLEM迭代下近似均匀分布。所提出的正电子成像技术可以进一步升级,以包括各种校正因子,并根据真实的o-Ps衰变模型进行修改。
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来源期刊
Bio-Algorithms and Med-Systems
Bio-Algorithms and Med-Systems MATHEMATICAL & COMPUTATIONAL BIOLOGY-
CiteScore
3.80
自引率
0.00%
发文量
3
期刊介绍: The journal Bio-Algorithms and Med-Systems (BAMS), edited by the Jagiellonian University Medical College, provides a forum for the exchange of information in the interdisciplinary fields of computational methods applied in medicine, presenting new algorithms and databases that allows the progress in collaborations between medicine, informatics, physics, and biochemistry. Projects linking specialists representing these disciplines are welcome to be published in this Journal. Articles in BAMS are published in English. Topics Bioinformatics Systems biology Telemedicine E-Learning in Medicine Patient''s electronic record Image processing Medical databases.
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