Clinical applications of PET in brain tumors

Malignant gliomas and metastatic tumors are the most common brain tumors. Neuroimaging plays a significant role clinically. In low-grade tumors, neuroimaging is needed to evaluate recurrent disease and tomonitor anaplastic transformation into high-grade tumors. In high-grade and metastatic tumors, the imaging chal-lenge is to distinguish between recurrent tumor and treatment-induced changes such as radiation necrosis. The current clinical gold standard, MRI, provides superior structural detail but poor specificity in identifying viable tumors in brain treated with sur-gery, radiation, or chemotherapy. 18F-FDG PET identifies ana-plastic transformation and has prognostic value. The sensitivity and specificity of 18F-FDG in evaluating recurrent tumor and treatment-induced changes can be improved significantly by coregistration with MRI and potentially by delayed imaging 3–8 h after injection. Amino acid PET tracers are more sensitive than 18F-FDG in imaging recurrent tumors and in particular recur-rent low-grade tumors. They are also promising in differentiating between recurrent tumors and treatment-induced changes