Localization of indium-111-immunoglobulin G, technetium-99m-immunoglobulin G and indium-111-labeled white blood cells at sites of acute bacterial infection in rabbits.

Biodistribution and infection imaging properties of 111In-DTPA-IgG, 99mTc-hydrazino nicotinamide-IgG and 111In-WBC were compared in rabbits with E. coli infection. Groups of six rabbits were injected with 10 mCi of 99mTc-IgG plus 0.5 mCi of 111In-IgG or 1 mCi of 99mTc-IgG plus 0.05 mCi of 111In-WBC. At 4-5 and 18-20 hr, dual photon scintigrams were acquired. At both times, the distributions of 99mTc and 111In-IgG were nearly identical. The sites of infection were well visualized with all three radiopharmaceuticals. In the early images, the target-to-background ratios (T/B) for 111In and 99mTc-IgG determined by ROI analysis were 1.95 +/- 0.26 and 2.57 +/- 0.38 (p = NS). In the delayed images, the T/B ratios increased (p < 0.01) to 3.56 +/- 0.49 and 4.90 +/- 0.98. At both times, the T/B ratios for 111In-WBC were higher (p < 0.01); 4.17 +/- 0.78 at 4-5 hr and 8.52 +/- 1.52 at 18-20 hr. These results indicate that all three agents yield excellent images of infection sites. Although 111In-WBC had higher T/B ratios, the ease of preparation of the radiolabeled proteins makes them attractive alternatives for infection imaging.