Positron emission tomography (PET) has been widely used for the diagnosis of serious diseases including cancer and Alzheimer's disease, based on the uptake of radiolabelled molecules that target certain pathological signatures. Recently, a novel imaging mode known as positronium lifetime imaging (PLI) has been shown possible with time-of-flight (TOF) PET as well. PLI is also of practical interest because it can provide complementary disease information reflecting conditions of the tissue microenvironment via mechanisms that are independent of tracer uptake. However, for the present practical systems that have a finite TOF resolution, the PLI reconstruction problem has yet to be fully formulated for the development of accurate reconstruction algorithms. This paper addresses this challenge by developing a statistical model for the PLI data and deriving from it a maximum-likelihood algorithm for reconstructing lifetime images alongside the uptake images. By using realistic computer simulation data, we show that the proposed algorithm can produce quantitatively accurate lifetime images for a 570~ps TOF PET system.

翻译：正电子发射断层扫描（PET）已广泛应用于包括癌症和阿尔茨海默病在内的重大疾病诊断，其原理基于靶向特定病理标志物的放射性标记分子摄取。近年来，一种名为正电子素寿命成像（PLI）的新型成像模式已被证明可借助飞行时间（TOF）PET实现。PLI具有实际意义，因为它能通过独立于示踪剂摄取的机制，提供反映组织微环境状态的互补疾病信息。然而，对于当前具有有限TOF分辨率的实际系统，PLI重建问题尚未得到充分形式化，难以开发精确的重建算法。本文通过建立PLI数据的统计模型，并推导出一种基于最大似然的算法来同时重建寿命图像与摄取图像，从而解决了这一挑战。基于真实计算机仿真数据，我们证明所提出的算法能够为570皮秒TOF PET系统生成定量准确的寿命图像。