Department of Physics, National and Kapodistrian University of Athens, Greece.
Department of Physics, National and Kapodistrian University of Athens, Greece; Institute of Accelerating Systems & Applications (IASA), Athens, Greece.
Comput Biol Med. 2023 Nov;166:107502. doi: 10.1016/j.compbiomed.2023.107502. Epub 2023 Sep 18.
Even though iterative methods and particularly Maximum Likelihood Expectation-Maximization (MLEM) algorithms have been established in reconstruction with Compton data, their detailed design with respect to physical rules and processes dominate their plain implementation in the form of a system matrix. A new elementary but efficient alternative for the well-known system matrix with respect to Compton Camera image reconstruction is presented in this work. For each detected event there is a weighting factor inserted as an accumulated probability which carries all the necessary information. This probability which involves only the Compton scattering angle of the incident photon corresponds to a map that correlates all events within all possible source origins. Based on maximizing likelihood principles, the proposed model weights in a stochastic way the difference of the scatterer-to-source angle θ, as it is determined by the deposited energy on the absorber, and any other potential scattering angle θ, specified by the position coordinates on the reconstruction matrix. Obtained image spatial resolution, angular distortions and response to focal length determination are a few of the studied cases for the algorithms' evaluation via simulations in GEANT4/GATE with a set of radioactive sources and phantoms with in- and out-of-plane arrangement.
尽管迭代方法，特别是最大似然期望最大化（MLEM）算法已经在康普顿数据重建中得到确立，但它们在物理规则和过程方面的详细设计主导了它们以系统矩阵形式的简单实现。在这项工作中，针对康普顿相机图像重建，提出了一种新的基本但有效的系统矩阵替代方案。对于每个检测到的事件，都会插入一个加权因子作为累积概率，其中包含所有必要的信息。这个概率只涉及入射光子的康普顿散射角，对应于一个关联所有可能源起源内所有事件的映射。基于最大似然原理，所提出的模型以随机方式加权散射角θ与源之间的差异，因为它由吸收体上沉积的能量决定，并且任何其他潜在散射角θ，由重建矩阵上的位置坐标指定。通过使用一组放射性源和具有内平面和外平面布置的体模在 GEANT4/GATE 中进行模拟，对算法进行了评估，研究了图像空间分辨率、角度失真和对焦距确定的响应等几个案例。
