Patients receive fluoromisonidazole F 18 ([^18F] FMISO) IV over 1 minute followed by PET scanning. Patients undergo a second [^18F] FMISO PET scan 4-8 weeks later. Patients who have not had a prior fludeoxyglucose F 18 ([^18F] FDG) PET scan as part of their routine clinical management undergo [^18F] FDG PET scanning at baseline. A subset of 10 patients undergo two [^18F] FMISO PET scans within a 48-hour period to evaluate the variability (test-retest) of this imaging measurement.