Abstract
18
Objectives To assess feasibility of 64Cu(Cu) in-vitro labeled leukocytes (WBC) for imaging inflammation, comparing it to 111In(In)WBC, 64Cu chloride (CuCl2) & 111In chloride (InCl2) in a rodent model.
Methods 13 adult Fisher 344 rats were divided into 4 groups: Group 1: CuWBC (n=4); Group 2: InWBC (n=3), Group 3: CuCl2 (n=3), Group 4: InCl2 (n=3). In Groups 1 & 2 donor rat WBCs were labeled. In Group 1, CuWBC labeling was performed as follows: WBCs were incubated in 5 mL saline with 10 μM DOTA ethyl ester & 150-185 MBq 64Cu-tropolone for 40 mins. at 37○C. The mixture was centrifuged at 450 g for 5 mins. Supernatant was decanted & cells resuspended in 3 mL normal saline. In Group 2, WBCs were labeled with 111In-oxine according to published methods. Labeling efficiency & cell viability were determined for Groups 1 & 2 at time of labeled WBC injection. Aseptic neutrophil mediated inflammation was induced in rats 24 hrs. before tracer injection by injecting 0.1 mL pure turpentine oil into the left thigh muscle. In all animals, 7.5 MBq activity was injected via the tail vein. Animals were sacrificed 24 hrs. later & tissue counting was performed. Activity/gram of inflamed (I) muscle was compared to activity/gram of normal (N) contralateral thigh muscle & ratios computed.
Results Labeling efficiency was similar for CuWBC & InWBC (91.2% vs. 89.6%, p=0.26); viability was slightly lower for CuWBC (96.2% vs. 98.7%, p=0.04). I/N ratio for CuWBC was similar to that for InWBC (p= 0.47). I/N ratios for CuWBC were higher than those for CuCl2 (p<0.0001) & InCl2 (p=0.0002). I/N ratios for InWBC also were higher than those for CuCl2 (p=0.06) & InCl2 (p=0.14) (table).
Conclusions These data indicate that 64Cu in vitro labeled leukocytes may be a useful PET agent for imaging inflammation & infection