Purpose: O-(2-[18F]fluoroethyl)-L-tyrosine (FET), a PET radiotracer of amino acid uptake, has shown potential for diagnosis and treatment planning in patients with glioblastoma (GBM). To improve quantitative assessment of FET PET imaging, we evaluated the repeatability of uptake of this tracer in patients with GBM.Methods: Test-retest FET PET imaging was performed on 8 patients with histologically confirmed GBM, who previously underwent surgical resection of the tumour. Data were acquired according to the protocol of a prospective clinical trial validating FET PET as a clinical tool in GBM. SUVmean, SUVmaxand SUV98%metrics were extracted for both test and retest images and used to calculate 95% Bland-Altman limits of agreement (LoA) on lesion-level, as well as on volumes of varying sizes. Impact of healthy brain normalization on repeatability of lesion SUV metrics was evaluated.Results: Tumour LoA were [0.72, 1.46] for SUVmeanand SUVtotal, [0.79,1.23] for SUVmax, and [0.80,1.18] for SUV98%. Healthy brain LoA were [0.80,1.25] for SUVmean, [0.80,1.25] for SUVmax, and [0.81,1.23] for SUV98%. Voxel-level SUV LoA were [0.76, 1.32] for tumour volumes and [0.80, 1.25] for healthy brain. When sampled over maximum volume, SUV LoA were [0.90,1.12] for tumour and [0.92,1.08] for healthy brain. Normalization of uptake using healthy brain volumes was found to improve repeatability, but not after normalization volume size of about 15 cm3.Conclusions Advances in Knowledge and Implications for Patient Care: Repeatability of FET PET is comparable to existing tracers such as FDG and FLT. Healthy brain uptake is slightly more repeatable than uptake of tumour volumes. Repeatability was found to increase with sampled volume. SUV normalization between scans using healthy brain uptake should be performed using volumes at least 15 cm3in size to ensure best imaging repeatability.

中文翻译：

---

定量18F-FET PET在成胶质细胞瘤中的可重复性。

目的：O-（2- [18F]氟乙基）-L-酪氨酸（FET）是一种氨基酸摄取的PET示踪剂，已显示出对胶质母细胞瘤（GBM）患者进行诊断和治疗计划的潜力。为了改善对FET PET成像的定量评估，我们评估了GBM患者使用该示踪剂的可重复性。方法：对8例经组织学证实为GBM的患者进行了再测试FET PET成像，这些患者先前曾接受过手术切除肿瘤。根据前瞻性临床试验的协议获取数据，验证FET PET作为GBM中的临床工具。提取了SUVmean，SUVmax和SUV98％指标，用于测试图像和重新测试图像，并用于计算病灶级别以及大小不同的体积的95％Bland-Altman一致极限（LoA）。结果：SUVmean和SUVtotal的肿瘤LoA分别为[0.72，1.46]，SUVmax的[0.79,1.23]和SUV98％的[0.80,1.18]。SUVmean的健康大脑LoA分别为[0.80,1.25]，SUVmax的[0.80,1.25]和SUV98％的[0.81、1.23]。肿瘤体积的体素水平SUV LoA分别为[0.76，1.32]和健康大脑的[0.80，1.25]。当以最大体积采样时，SUV LoA的肿瘤[0.90,1.12]和健康的大脑[0.92,1.08]。使用健康的大脑体积对摄取量进行归一化可改善可重复性，但在归一化体积约15 cm3后不会改善。结论知识进步和对患者护理的意义：FET PET的可重复性可与现有示踪剂（如FDG和FLT）相媲美。健康的大脑摄取比肿瘤体积的摄取具有更高的可重复性。发现重复性会随着采样量的增加而增加。使用健康的大脑摄取进行的两次扫描之间的SUV归一化应使用至少15 cm3的体积进行，以确保最佳的成像重复性。