The plan for this study involves the non-therapeutic administration of a radiopharmaceutical, N-13 ammonia or F-18 fluorodeoxyglucose, one to two doses, during the tumor ablation procedure. The perfusion PET scan is a diagnostic imaging test. The tumor ablation procedure is performed according to our standard clinical practice and is not itself a research activity. The use of N-13 ammonia or F-18 fluorodeoxyglucose to image liver perfusion with a PET scanner is the research portion of the procedure. The patient will receive one or two doses of N-13 ammonia (10 mCi (millicurie)/dose) for intraprocedural assessment of ablation results. Not more than two doses will be administered and one or both doses will be administered on the day of the tumor ablation procedure only. The ammonia perfusion scan will not be used to change or modify the ablation procedure.