PET imaging of gliomas using novel tracers: a sleeping beauty waiting to be kissed.

" Precise tumor localization and exact delineation from surrounding healthy brain tissue is of the utmost importance for planning tumor resection and/or radiation therapy, as well as for assessment of tumor recurrence after primary therapy. " Approximately 1–2% of all tumors are brain tumors. Gliomas represent 45% of all brain tumors (50% being highly malignant), followed by meningiomas (27%), with an incidence of 2–16/100,000 [1]. The American Cancer Society estimated that, in 2005, primary brain tumors were the cause of death of approximately 12,760 women and men [2,3]. Precise tumor localization and exact delinea-tion from surrounding healthy brain tissue is of the utmost importance for planning tumor resection and/or radiation therapy, as well as for assessment of tumor recurrence after primary therapy. Moreover, novel targeted therapeutics mainly used after primary resection and radiation therapy lead to an increasing demand for functional and molecular imaging techniques for assessment of therapeutic response. MRI, at present, is still the gold standard in the primary diagnosis of brain tumors. Conventional morphological MRI provides information with respect to size and localization as well as additional insights on secondary pheno mena, that is edema and bleeding, which cannot be supplied in the same quality by PET [4]. However, the specific-ity for the differentiation of vital tumor tissue versus inf lammatory processes, edema and reactive changes, is limited. Moreover, tumor borders determined by the use of contrast-enhanced MRI often under-or overestimate the true extent of the tumor [5,6]. It is our firm belief, that in this respect the molecular information of PET using novel tracers provides vital information in combination with classical neuroimaging techniques, such as MRI and computed tomography (CT). In addition, functional MRI techniques including diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS), diffusion-tensor imaging (DTI), dynamic contrast-enhanced imaging (DCE-MRI) and dynamic susceptibility imaging (DSC MRI) are in this context , in our opinion, not competing but complementary modalities to PET. While PET and PET/CT using the tracer 18 F-f luorodeoxyglucose (18 F-FDG) has become a success story for many tumors outside the CNS, the unfavorable characteristics of 18 F-FDG in the CNS have hampered its success for imaging of brain tumors. While brain tumors, like other tumors, may show an increased glucose metabolism, which can be visualized and quantified with 18 F-FDG, the major disadvantage of 18 F-FDG for the diagnosis of a brain tumor is the high background uptake caused by the high glucose …