This is a ten subject, phase 1 study. The purpose of the study is to demonstrate drug safety in a group with high grade brain tumors and to evaluate cell proliferation with F-18 FLT. FLT is known to clear out of normal brain and detect brain tumor. This population represents a potential clinical population that may benefit from this PET imaging tracer. This information will help improve the design and conduct of future F-18 FLT clinical trials.