【作者】 顾峥； 康晓文； 孙熙杉； 吴朝霞； 王石； 刘亚强； 金永杰；

【Author】 GU Zheng KANG Xiao-wen SUN Xin-shan WU Zhao-xia WANG Shi LIU Ya-qiang JIN Yong-jie (Department of engineering physics,THU,Beijing,100084,China)

【机构】 清华大学工程物理系；

【摘要】 小动物PET前端探测器由1800个锗酸铋闪烁体BGO(Bi₄Ge₃O₁₂)晶体模块,每个模块按照一定的分光原理被切割成8×8个像素单元,同时在该晶体模块后耦合4个光点倍增管（PMT）,光电倍增管通过基于位置权重法的电子学电路来进行位置辨别,从而分辨出8×8个不同的像素单元。本文首先介绍了一种基于模糊聚类方法中的模糊C均值聚类算法,用于晶体位置识别,初步的结果显示该方法对于像素点交联的情况具有较快的速度以及较好的适应性。本文后一部分对该方法进行了一定的改进,提出了DFCM的算法。更多还原

【Abstract】 A high resolution detector is being developed for our small animal position emission tomography(MicroPET).The detector unit consist of 8×8 crystal blocks,coupled to four photomultiplier tubes(PMTs).Each scintillation event is mapped in a two dimensional(2-D)position through the relative ratio of the output signals of the PMTs.Crystal Look-up table(CLT) used in ThuMicroPET scanner defines the matching relation between signal position of a detected event to a corresponding detector pixel location.It has a direct impact on imaging quality and brings significant influence to the gantry overall performance.However,the currently used method involves a lot of human interaction for CLT corrections,and cannot be implemented as a general process due to its complexity.This paper introduces a fast accuracy method based on Fuzzy C-Means (FCM)Clustering Algorithm for crystal identification.In the FCM,a cluster center and a fuzzy partition matrix of individual events in the 2-D position are defined.By iteratively updating the cluster centers and the membership grades for each event,we can move the cluster center to the right location in a short time,based on minimizing objective function that represents the distance from any given events to a cluster center weighted by its membership grade.The preliminary result shows that FCM can be used effectively in CLT construction,which significantly reduces the time,and brings excellent accuracy than we expected.In latter part of this paper,we improve the method of FCM and come up with the DFCM algorithm.更多还原