99Tcm-phenylene imine phenol as a potential leukocyte labelling agent

The aim of this study was to evaluate 99Tcm-labelled phenylene imine phenol (99Tcm-Ph(IP)2) as a leukocyte label. The 99Tcm complex exhibits a neutral lipophilic character. The radiochemical purity of the 99Tcm-Ph(IP)2 was high both soon after labelling (94.5 +/- 1.2%, n = 7) and at 24 h (89.7 +/- 1.0%, n = 7). In a comparative study, the labelling efficiency of 99Tcm-Ph(IP)2 and 99Tcm-hexamethylpropylene amine oxime (99Tcm-HMPAO) labelled leukocytes was 47.1 +/- 3.5% (n = 7) and 58.5 +/- 7.0% (n = 7) respectively. The viability of labelled leukocytes was greater than 90% for both 99Tcm complexes. The elution ratios of labelled leukocytes with 99Tcm-Ph(IP)2 at 1, 4 and 24 h were 10.1 +/- 3.5%, 17.2 +/- 2.7% and 23.0 +/- 2.4% (n = 7) respectively, while those with 99Tcm-HMPAO were 10.8 +/- 1.2%, 18.3 +/- 2.0% and 37.0 +/- 3.7% (n = 7) respectively. In conclusion, 99Tcm-Ph(IP)2, with good stability and significant leukocyte labelling efficiency, is a potential leukocyte label.