PET Center and Translational Imaging Laboratory, Children's Hospital of Michigan, Detroit, MI, USA.
J Neurooncol. 2013 Mar;112(1):121-32. doi: 10.1007/s11060-013-1043-4. Epub 2013 Jan 9.
Pretreatment delineation of infiltrating glioma volume remains suboptimal with current neuroimaging techniques. Gadolinium-enhanced T1-weighted (T1-Gad) MR images often underestimate the true extent of the tumor, while T2-weighted images preferentially highlight peritumoral edema. Accumulation of α-[(11)C]methyl-L-tryptophan (AMT) on positron emission tomography (PET) has been shown in gliomas. To determine whether increased uptake on AMT-PET would detect tumor-infiltrated brain tissue outside the contrast-enhancing region and differentiate it from peritumoral vasogenic edema, volumes and spatial concordance of T1-Gad and T2 MRI abnormalities as well as AMT-PET abnormalities were analyzed in 28 patients with newly-diagnosed WHO grade II-IV gliomas. AMT-accumulating grade I meningiomas were used to define an AMT uptake cutoff threshold that detects the tumor but excludes peri-meningioma vasogenic edema. Tumor infiltration in AMT-accumulating areas was studied in stereotactically-resected specimens from patients with glioblastoma. In the 28 gliomas, mean AMT-PET-defined tumor volumes were greater than the contrast-enhancing volume, but smaller than T2 abnormalities. Volume of AMT-accumulating tissue outside MRI abnormalities increased with higher tumor proliferative index and was the largest in glioblastomas. Tumor infiltration was confirmed by histopathology from AMT-positive regions outside contrast-enhancing glioblastoma mass, while no or minimal tumor cells were found in AMT-negative specimens. These results demonstrate that increased AMT accumulation on PET detects glioma-infiltrated brain tissue extending beyond the contrast-enhanced tumor mass. While tryptophan uptake is low in peritumoral vasogenic edema, AMT-PET can detect tumor-infiltrated brain outside T2-lesions. Thus, AMT-PET may assist pretreatment delineation of tumor infiltration, particularly in high-grade gliomas.
目前的神经影像学技术对浸润性脑胶质瘤的术前勾画仍不理想。钆增强 T1 加权（T1-Gad）磁共振成像常低估肿瘤的真实范围，而 T2 加权图像则优先突出瘤周水肿。正电子发射断层扫描（PET）示踪剂 α-[(11)C]甲基-L-色氨酸（AMT）在脑胶质瘤中呈高摄取。为明确 AMT-PET 摄取增加是否可检测到增强区以外的肿瘤浸润脑组织，并与瘤周血管源性水肿相鉴别，对 28 例新诊断的 WHO Ⅱ-Ⅳ级脑胶质瘤患者的 T1-Gad 和 T2 磁共振异常以及 AMT-PET 异常的体积和空间一致性进行了分析。用 AMT 摄取增高的Ⅰ级脑膜瘤来确定一个 AMT 摄取截断值，该值可检测到肿瘤，但不包括脑膜瘤周围的血管源性水肿。对胶质母细胞瘤患者立体定向切除标本中 AMT 摄取区的肿瘤浸润进行了研究。在 28 例脑胶质瘤中，平均 AMT-PET 定义的肿瘤体积大于增强体积，但小于 T2 异常。在 MRI 异常外的 AMT 摄取组织体积随肿瘤增殖指数的增加而增大，在胶质母细胞瘤中最大。在增强的胶质母细胞瘤瘤体外 AMT 阳性区域的组织学证实有肿瘤浸润，而 AMT 阴性标本中则无或很少有肿瘤细胞。这些结果表明，PET 上 AMT 摄取增加可检测出超出增强肿瘤团块的胶质瘤浸润脑组织。虽然瘤周血管源性水肿中的色氨酸摄取较低，但 AMT-PET 可检测到 T2 病变外的肿瘤浸润脑组织。因此，AMT-PET 可能有助于术前肿瘤浸润的勾画，特别是在高级别脑胶质瘤中。
