A COMPARATIVE-STUDY OF 99TCM-HMPAO AND 99TCM-ECD AS A LEUKOCYTE LABELING AGENT

An attempt was made to use Tc-99m-ethyl cysteinate dimer (Tc-99m-ECD) (Neurolite, Du Pont Merck, N. Billerica, MA) to label leukocytes. The radiochemical purity of Tc-99m-ECD, labelling efficiency of leukocytes , cell viability of labelled leukocytes and stability of Tc-99m-ECD-la belled leukocytes were calculated. Compared with the commercial cell-l abelling agent, Tc-99m-hexamethylpropyleneamine oxime (Tc-99m-HMPAO): (1) the radiochemical purity of Tc-99m-ECD was higher than that of Tc- 99m-HMPAO and at immediately, 1, 2, 4, 6, 8 and 24 h after Tc-99m labe lling; (2) the labelling efficiency of Tc-99m-ECD-labelled leukocytes was lower than that of Tc-99m-HMPAO; (3) the viability of the labelled white blood cells (WBC) was high for both agents; and (4) the stabili ty of Tc-99m-ECD-labelled leukocytes was worse than that of Tc-99m-HMP AO at 1, 2, 4, 6, 8 and 24 h. It is concluded that although Tc-99m-ECD is more stable than Tc-99m-HMPAO, because of the lower labelling effi ciency and poorer stability of Tc-99m-ECD-labelled leukocytes, Tc-99m- ECD is not a good choice as a leukocyte-labelling agent to replace com mercial Tc-99m-HMPAO.