The reproducibility of time-of-flight PET and conventional PET for the quantification of myocardial blood flow and coronary flow reserve with 13N-ammonia
The reproducibility of time-of-flight PET and conventional PET for the quantification of myocardial blood flow and coronary flow reserve with 13N-ammonia
复制标题
飞行时间 PET 和传统 PET 定量 13N-氨心肌血流量和冠状动脉血流储备的重现性
DOI：
10.1007/s12350-015-0098-3
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发表时间：
2015
影响因子：
2.4
通讯作者：
Takeshi Tomiyama
中科院分区：
文献类型：
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作者：
Masaya Suda;Masahisa Onoguchi;Takeshi Tomiyama
正电子发射断层扫描（PET）系统最近取得了重大进展，可以提高灵敏度，空间分辨率和降噪。这样的进步提供了更好质量的心肌灌注图像，具有更低的注射剂量，因此对患者的辐射更低。此外，预计心肌血流量（MBF）和冠状动脉血流储备（CFR）的更好的量化。1-7许多新的PET相机具有利用飞行时间（TOF）技术的三维（3D）模式采集。3D采集中的系统灵敏度远大于2D采集。另一方面，背景活动的分数在3D中也更高。另一方面，8 TOF可以通过降低噪声来显著地增加信噪比。8 TOF可以估计511 keV光子的到达时间，因此，发射点的位置可以沿着两个检测器对之间的响应线被约束。9，10为了实现TOF的充分效果，需要具有高时间分辨率的闪烁探测器。允许最近TOF PET发展的主要因素是新闪烁材料的可用性，例如LSO和LYSO。此外，TOF PET在宽视场全身成像方面比脑成像具有更大的优势。许多报道表明TOF PET在肿瘤学领域的临床价值。另一方面，有限数量的报告报道了TOF PET在心脏成像中的临床价值。11，12心脏PET可能需要对系列示踪剂浓度进行可靠的定量，因此，它通常用于估计MBF、CFR以及各种代谢和分子功能作为定量参数，例如葡萄糖代谢率、转运蛋白保留指数、受体密度等。在不久的将来进行治疗监测。马萨亚等人在本期杂志中评估了使用N-13氨PET进行3D采集和TOF时MBF和CFR的再现性。13体模研究显示TOF采集的部分容积效应较小，图像对比度高于非TOF采集。这种改善在较大的视场中比在较小的视场中表现得更好。从TOF概念出发，这种结果是相当合理的。此外，临床数据也显示出较高的重现性，使用TOF技术的观察者内以及观察者间的变异性较小。不幸的是，该再现性研究不是基于两个单独的采集方案设计的。然而，很好地证明了MBF和CFR值的小的观察者内和观察者间变异性，这可能是由于更高的目标-背景比和更少的部分容积效应。有趣的是，作者指出了在有和没有TOF采集的情况下，右心室附近心尖和节段的变化可能存在差异。来自右心室的较高背景噪声可能会导致无TOF的变化。另一方面，没有明确的解释为什么TOF可以减少心尖MBF值的变化。TOF可以显着改善部分容积效应，特别是在厚度较小以及顶端区域的周边视野中。
A significant progress in positron emission tomography (PET) system has recently been seen which may improve sensitivity, spatial resolution, and noise reduction. Such progress has provided better quality of myocardial perfusion images with lower injected dose, and thus lower radiation to the patient. In addition, better quantification of myocardial blood flow (MBF) and coronary flow reserve (CFR) is expected. 1–7 Many of new PET cameras have three-dimensional (3D) mode acquisition with time-of-flight (TOF) technology. The system sensitivity in 3D acquisition is much greater than 2D acquisition. On the other hand, the fraction of background activity is also higher in 3D. 8 TOF, on the other hand, may significantly increase signal-to-noise ratio by decreasing noise. 8 TOF can estimate the arrival time of the 511 keV photons, and therefore, the location of the emission point may be constrained along a line-of-response between the two detector pairs. 9, 10 In order to perform adequate effects of TOF, a scintillation detector with high time resolution is required. The main factor that permits recent TOF PET development is the availability of new scintillation materials, such as LSO and LYSO. In addition, TOF PET has gained greater advantages in whole-body imaging with wide field of view than the brain imaging. A number of reports indicated clinical value of TOF PET in oncology fields. On the other hand, limited number of reports have reported clinical value of TOF PET in cardiac imaging. 11, 12 Cardiac PET may require reliable quantification of serial tracer concentrations, and thus, it is often used to estimate MBF, CFR, and various metabolic and molecular functions as quantitative parameters, such as metabolic rate of glucose, transporter retention index, receptor density, etc. Such cardiac functional assessment using optimal PET parameters is expected to be applied for severity assessment, treatment planning, and treatment monitoring in the near future. Masaya et al in the current issue assessed reproducibility of MBF and CFR with N-13 ammonia PET under 3D acquisition with and TOF. 13 The phantom study showed smaller partial volume effect with higher image contrast with TOF acquisition than non TOF. Such improvement was better seen in larger field of view than smaller field of view. Such results are quite reasonable on the basis of TOF concept. In addition, clinical data also showed higher reproducibility with smaller intra-as well as inter-observer variability using TOF technique. Unfortunately, this reproducibility study was not designed based on two separate acquisition protocols. However, small intra-as well as inter-observer variability of MBF and CFR values was well demonstrated, probably due to higher target-to-background ratio and less partial volume effects. Interestingly, the authors pointed out possible differences in variation in the apex and the segments near the right ventricle with and without TOF acquisitions. Higher background noise from the right ventricle may cause variations without TOF. On the other hand, there are not clear explanations why TOF may reduce variation of MBF value in the apex. Partial volume effects may significantly be improved by TOF, particularly in smaller thickness and also peripheral field of view for apical areas.