Molecular imaging of regional brain tumor biology

Energy metabolism measurements in gliomas in vivo are now performed widely with positron emission tomography (PET). This capability has developed from a large number of basic and clinical science investigations that have cross fertilized one another. This article presents several areas that exemplify questions that have been explored over the last two decades. While the application of PET with [(18)F]-2-fluoro-2-deoxyglucose (FDG-PET) has proven useful for grading and prognosis assessments, this approach is less clinically suitable for assessing response to therapy, even though results to date raise very intriguing biological questions. Integration of metabolic imaging results into glioma therapy protocols is a recent and only preliminarily tapped method that may prove useful in additional trials that target DNA or membrane biosynthesis, or resistance mechanisms such as hypoxia. There are exciting future directions for molecular imaging that will undoubtedly be fruitful to explore, especially apoptosis, angiogenesis and expression of mutations of genes, e.g., epidermal growth factor receptor, that promote or suppress cellular malignant behavior.