[en] The authors have compared the standard Tc-99m DTPA and Tc-99m HMPAO studies for evaluating brain cell viability and brain death. Thirteen studies were performed on 12 patients with various diseases, including four head traumas, three strokes, one acquired immunodeficiency syndrome (AIDS), one adult respiratory disease syndrome (ARDS), one meningitis, one hypoglycemic coma, and one cerebral infarct. All were on life-support systems. Each received 20 mCi Tc-99m DTPA for cerebral flow and blood pool studies. Then, 20 mCi Tc-99m HMPAO was given for flow study and tissue phase images