Abstract: STUDIES ON THE ELECTRONIC STRUCTURES ANDRETENTION MECHANISM of99TcmBRAIN IMAGING AGENTAuthor Zhang HuabeiLiu Boli (Department of chemistry, Beijing Normal University,Beijing 100875) ABSTRACT The electronic structures of99Tcmcomplexes are calculated by SCCDVXa method,and the retention mechanism is discussed. The results indicate the retention of 99Tcmcomplexes in the brain is dependent on their LUMO energy levels and instability. The higher their LUMO energy levels are,the better their retention in the brain is.And the weakening of the bond between Tc and the nitrogen atom of dioxime causes them more unstable, this might also lead to the better retention in the brain. Key words SCCDVXa method99Tcmbrain imaging agentRetention mechanism