Abstract: STUDIES ON THE KINETICS OF ~(99)Tc~m-d,l-HMPAO DECOMPOSITION AND THE METHOD OF STABILIZATIONZHANG JINMING；TIAN JIAHE（The Chinese PLA General Hospital, Beijing,1000853）LIN QIONGFANG；JIN XIAOGAI（China Institute of Atomic Energy, P.O.Box 275，Beijing，102413）ABSTRACT The kinetics of ~(99)Tc~m-d，l-HMPAO decomposition is studied using hon1e kits. The resultsshow that ~(99)Tc~m-d，l-HMPAO decomposition is a first-order reaction， The decomposition con-stant k is found to be 0．017±0． 007h~(-1) under the experimental conditions of 20℃，185MBq／ml，pH 7．0．The stability of ~(99)Tc~m-d，l-HMPAO is affected not only by pH and radioactive concen-tration， but also by temperature. Using gentisic acid as a stabilizer，740MBq／ml of ~(99)Tc~m-d，l-HMPAO can be stabilized for 3h with the radiochemical purity above 80％.Key words ~(99)Tc~m-d，l-HMPAO Kinetics of decomposition reaction Reaction rate constant Stabilizer