Abstract: PREPARATION OF BRAIN PERFUSION IMAGING AGENT 99TcmECD WITH EDTA EXCHANGE REACTION——STUDY ON THE REACTION CONDITIONSJia Shaowei(The Second Affiliated Hospital, Medical College of Jinan University, Shenzhen 518020)Zhu Lin(National Research Centre for Certified Reference Material，s, Beijing 100013)Abstract In order to improve ECD kit formulation and select the best labeling condition, the radiochemical purity and lipophilic fraction of 99TcmECD in different labeling conditions are observed. The results show that 99TcmECD prepared by EDTA ligand exchange reaction is very stable, the radioactivity doesn，t influence the radiochemical purity and lipophilic fraction, the best pH limits is ranged from 5 to 8， and 360 μg EDTA amounts with 2～6 mL volume is suitable. 99TcmECD can reserve stably in different pH buffer solutions.Key words EDTA 99TcmECD lipohilic fraction exchange reaction