Accurately defining glioma infiltration is crucial for optimizing radiotherapy and surgery, but glioma infiltration is heterogeneous and MRI imperfectly defines the tumor extent. Currently, it is impossible to determine the tumor infiltration gradient within a FLAIR signal. O-(2-[18F]fluoroethyl)-L-tyrosine (FET)-PET often reveals high-grade glioma infiltration beyond contrast-enhancing areas on MRI. Here, we studied FET uptake dynamics in tumor and normal brain structures by dual-timepoint (10 min and 40–60 min post-injection) acquisition to optimize analysis protocols for defining glioma infiltration. Over 300 serial stereotactic biopsies from 23 patients (mean age 47, 12 female/11 male) of diffuse contrast-enhancing gliomas were taken from areas inside and outside contrast enhancement or outside the FET hotspot but inside FLAIR. The final diagnosis was G4 in 11, grade 3 in 10, and grade 2 in 2 patients. The target-to-background (TBRs) ratios and standardized uptake values (SUVs) were calculated in areas used for biopsy planning and in background structures. The optimal method and threshold values were determined to find a preferred strategy for defining glioma infiltration. Standard thresholding (1.6× uptake in the contralateral brain) in standard acquisition PET images differentiated a tumor of any grade from astrogliosis, although the uptake in astrogliosis and grade 2 glioma was similar. Analyzing an optimal strategy for infiltration volume definition astrogliosis could be accurately differentiated from tumor samples using a choroid plexus as a background. Early acquisition improved the AUC in many cases, especially within FLAIR, from 56% to 90% sensitivity and 41% to 61% specificity (standard TBR 1.6 vs. early TBR plexus). The current FET-PET evaluation protocols for contrast-enhancing gliomas are limited, especially at the tumor border where grade 2 tumor and astrogliosis have similar uptake, but using choroid plexus uptake in early acquisitions as a background, we can precisely define a tumor within FLAIR that was outside of the scope of current FET-PET protocols.
准确定义胶质瘤浸润范围对于优化放疗和手术方案至关重要，但胶质瘤浸润具有异质性，且磁共振成像（MRI）无法完美界定肿瘤边界。目前尚无法在FLAIR信号区域内确定肿瘤浸润梯度。O-(2-[18F]氟乙基)-L-酪氨酸（FET）-PET常能检测到MRI对比增强区域外的高级别胶质瘤浸润。本研究通过双时间点（注射后10分钟及40-60分钟）采集技术，分析肿瘤与正常脑组织的FET摄取动力学特征，以优化界定胶质瘤浸润范围的影像分析方案。我们对23例弥漫性对比增强胶质瘤患者（平均年龄47岁，女12例/男11例）进行了超过300次连续立体定向活检，取样区域涵盖对比增强区内、外及FET热点区外但FLAIR信号区内。最终诊断为4级胶质瘤11例，3级10例，2级2例。在活检规划区域及背景结构中分别计算靶本比（TBRs）与标准化摄取值（SUVs），通过确定最佳分析方法与阈值，探索界定胶质瘤浸润范围的优选策略。标准采集PET图像采用常规阈值（对侧脑组织摄取的1.6倍）可区分任何级别肿瘤与星形胶质细胞增生，但后者与2级胶质瘤的摄取特征相似。以脉络丛为背景值制定浸润体积界定方案时，可准确区分星形胶质细胞增生与肿瘤样本。早期采集在多数情况下提升了受试者工作特征曲线下面积（AUC），特别是在FLAIR信号区内，灵敏度从56%提升至90%，特异性从41%提升至61%（标准TBR 1.6阈值 vs 早期脉络丛TBR阈值）。当前针对对比增强胶质瘤的FET-PET评估方案存在局限，尤其在肿瘤边界区域，2级胶质瘤与星形胶质细胞增生的摄取特征相似。但采用早期采集的脉络丛摄取值作为背景参考，我们能够精确定义FLAIR信号区内的肿瘤范围，这突破了现有FET-PET方案的检测局限。
肿瘤(癌症)患者之家