CNS Brain Metastasis; Head and Neck Cancer; Lung Cancer; Prostate Cancer; Esophageal Cancer
Interventions:
Procedure: Imaging with 18F-FLT PET; Procedure: Imaging with 18F-FLT PET; Procedure: Imaging with 18F-FLT PET; Procedure: Imaging with 18F-FLT PET; Procedure: Imaging with 18F-FLT PET