IN VITRO EVALUATION OF CANINE GRANULOCYTES LABELED WITH 99mTC‐HEXAMETHYLPROPYLENEAMINE OXIME:

Technetium‐99m hexamethylpropyleneamine oxine ( 99m Tc‐HMPAO) and Indium‐111 oxine ( 111 In‐oxine) labeled canine gramulocytes were evaluated in vitro over a six hour period. Labeling efficiency for 99m TC‐HMPAO and 111 In‐oxine labeled granulocytes was 39.6%± 8.0% and 60.6%± 17.6% (mean ± SD) respectively. The mean in vitro elution of the radiolabel ranged from 8.7‐14.0% for the 99m Tc‐HMPAO grannulocytes and from 6.1‐9.0% for the 111 In‐oxine granulocytes. Mean cell viability, for the 99m Tc‐HMPAO, 111 In‐oxine and non‐radiolabeled control granulocytes ranged from 97.8‐99.4%, 96.4‐98.5% and 98.2‐99.0%, respectively. The phagocytic ability of the 99m Tc‐HMPAO, 111 In‐oxine and control granulocytes ranged from 47.5‐54.1%, 38.9‐56.2% and 46.6‐57.8% respectively over the six hour study period. Although labeling efficiency using 111 In‐oxine was significantly (P=0.05) better than 99m Tc‐HMPAO, there was no significant difference in label retention of the two radiolabels. There was no significant difference in viability or phagocytic function during the six hour study period. Considering the potential cost advantage and the superior imaging qualities of Technetium‐99m relative to Indium‐111, 99m Tc‐HMPAO appears to be a good alternative to 111 In‐oxine as a granulocyte label.