fluorine F 18 EF5 A radioconjugate consisting of EF5, a fluorinated derivative of etanidazole, conjugated to fluorine F 18, a positron emitting isotope. EF5 binds to hypoxic tissue; conjugation to Fluorine F 18 allows imaging of hypoxic regions within tumors. Check for active clinical trials or closed clinical trials using this agent. (NCI Thesaurus)