Utilization of Lutetium Background Radiation for Quantitative Total-Body PET Imaging

项目总结/摘要 正电子发射断层扫描（PET）被广泛用作诊断、预后和诊断的临床和研究工具。 肿瘤学中的治疗计划，同时越来越多地被采用在其他领域，如心脏病学，神经病学， 和炎症性疾病。最新一代的PET扫描仪提供了显着增强的灵敏度 具有增加的轴向成像范围。这些扫描仪中的灵敏度增益直接转化为改进的 标准成像协议中的成像质量，并允许使用具有超短时间帧的新扫描协议 或超低剂量扫描。这些系统中的长轴向视场（AFOV）提供了独特的机会， 解决PET中量化障碍的挑战。在影响定量的各种因素中， 由于PET的准确性，来自衰减、散射和人体运动的影响是常见和主要的。在这 项目中，我们的目标是利用这些扫描仪中存在的镥（Lu）背景辐射：首先，用于衰减 校正（AC）和散射校正（SC），第二，用于运动校正（MC），特别注意 超低剂量PET扫描AC和SC通常使用从以下获得的衰减图（μ图）进行： 在PET之前进行的计算机断层扫描（CT）。随着超低剂量PET扫描成为可能 对于长AFOV PET扫描仪，希望通过估计μ图来进一步降低辐射剂量， 当可以避免额外的CT扫描时，Lu背景辐射。我们将主要研究 uEXPLORER扫描仪是世界上第一台全身PET扫描仪， 同时对整个身体进行成像，并将Lu背景数据与PET发射一起使用 衰减和活动的最大似然重建（MLAA）中的数据。我们希望能够改善 与先前的研究相比，定量准确度高，因为灵敏度高，背景辐射通量增加 源自长AFOV PET扫描仪中的大量基于Lu的探测器，除了 在单个床位置扫描整个身体，使得能够更有效地利用Lu背景。最后， 由于人体运动通过引入图像模糊和衰减-发射失配而导致量化偏差， 我们将使用数据驱动的全身MC框架来校正基于Lu背景的μ图和 PET图像。我们将在两种情况下研究不同类型的运动对PET量化的影响：首先，当 PET发射数据被用于运动估计，第二，利用Lu背景数据的可行性， 运动估计，特别是在超低剂量扫描或具有低放射性示踪剂摄取的身体区域中，其中 标准的基于发射的数据驱动的运动估计方法易于出错。这一点尤其重要 在全身PET中，因为身体一个区域中的运动可能影响其他区域中的AC和SC。我们相信这 这一贡献将提高新一代PET扫描仪的量化和诊断能力， 将使超低剂量PET的临床和研究应用更加广泛，特别是在敏感人群中 例如婴儿、儿童和青少年，从而更好地了解人类健康。

Project Summary/Abstract Positron emission tomography (PET) is widely used as a clinical and research tool for diagnosis, prognosis, and treatment planning in oncology, while increasingly being adopted in other fields such as cardiology, neurology, and inflammatory disorders. The latest generation of PET scanners offer significant enhancements in sensitivity with an increased axial imaging extent. The sensitivity gain in these scanners directly translates into improved image quality in standard imaging protocols and enables use of new scan protocols with ultrashort time frames or ultralow-dose scans. The long axial-field-of-view (AFOV) in these systems offers unique opportunities and challenges in addressing quantification barriers in PET. Among a wide range of factors affecting the quantitative accuracy of PET, the effects from attenuation, scatter, and human motion are common and predominant. In this project, we aim to utilize the lutetium (Lu) background radiation present in these scanners: first, for attenuation correction (AC) and scatter correction (SC), and second, for motion correction (MC), with particular attention on ultralow-dose PET scans. AC and SC are usually performed using the attenuation maps (μ-maps) obtained from a computed tomography (CT) scan performed prior to PET. As ultralow-dose PET scans are now made possible with long-AFOV PET scanners, it is desirable to further reduce the radiation dose by estimating the μ-maps from the Lu background radiation, when an additional CT scan can be avoided. We will primarily study our methodology with the uEXPLORER scanner, which is the world’s first total-body PET scanner that can simultaneously image the entire body, and will employ the Lu background data together with the PET emission data in maximum likelihood reconstruction of attenuation and activity (MLAA). We expect to achieve improved quantitative accuracy compared to prior studies as the high sensitivity and increased flux of background radiation originating from the large volume of Lu-based detectors in long-AFOV PET scanners, in addition to the ability of scanning the entire body in a single bed position, enables more efficient utilization of the Lu background. Finally, as human motion causes quantification bias by introducing image blurring and attenuation-emission mismatches, we will use a data-driven total-body MC framework to correct both the Lu-background-based μ-maps and the PET images. We will study the effects of different types of motion on PET quantification in two cases: first, when PET emission data is used for motion-estimation and second, feasibility of utilizing the Lu background data in motion-estimation, particularly in ultralow-dose scans or body regions with low radiotracer uptake, in which standard emission-based data-driven motion estimation methods are prone to error. This is especially important in total-body PET, as motion in one region of body could affect the AC and SC in other regions. We believe this contribution will improve the quantification and diagnosis capability in the new generation of PET scanners and will enable wider clinical and research applications of ultralow-dose PET, particularly in sensitive populations such as infants, children, and adolescents, leading to better understanding of human health.