A high-efficiency, rapid and multi-dose procedure for white blood cell labelling with 99Tcm-HMPAO

99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO) is presently recognized as an effective radiopharmaceutical for in vitro white blood cell (WBC) labelling in addition to its widespread utility in cerebral blood flow imaging. While performing clinical studies in patients with a wide range of inflammatory diseases, the effect of the ligand and stannous ion quantity on the labelling efficiency (LE) of WBC was examined. A mean LE of 64 +/- 7% (n = 29) was achieved when the whole HMPAO kit was used for labelling. The LEs were 78 +/- 5% (n = 43), 83 +/- 3% (n = 37) and 85 +/- 5% (n = 18) when one-half, one-third and one-fifth of the lyophilized kit was used, respectively. This is in agreement with the reports of Sampson et al. and Lang et al., suggesting that the optimal formulation of the 99Tcm-HMPAO is a faction of the whole kit. Accordingly, fractionation of a freshly prepared 99Tcm-HMPAO kit into five parts for a high-efficiency WBC labelling is proposed, encouraging the more widespread use of 99Tcm-HMPAO in WBC labelling.