Renal cortical perfusion in rabbits: visualization with color amplitude imaging and an experimental microbubble-based US contrast agent.

Abstract

To evaluate an experimental microbubble-based ultrasound (US) contrast agent (Imagent US, formulation AF0150) in the kidney to help identify focal perfusion abnormalities. Six incremental doses (0.007-0.2 mL/kg) of contrast material were injected intravenously in six New Zealand rabbits (3.1-3.5 kg), with experimental focal renal ischemia in five kidneys. Unenhanced and contrast material-enhanced color amplitude and gray-scale images of the kidney were analyzed for changes in mean pixel intensity. Kidneys were harvested and examined pathologically. On contrast-enhanced color amplitude images, mean pixel intensity increased significantly in cortex and medulla at every dose level (P < .0005) (with doses as low as 0.007 mL/kg), and differences were significant in cortical peak intensity and duration of enhancement with incremental increases in dose (P < .006). On contrast-enhanced gray-scale images, renal cortical enhancement reached statistical significance only at the highest dose (0.2 mL/kg). Duration of gray-scale tissue enhancement was not dose related. Color mean pixel intensity markedly increased in areas of normally perfused kidney (P = .002) but remained essentially unchanged in ischemic areas (P = .34). Color Doppler and gray-scale images enhanced with this microbubble-based US contrast agent depict renal cortical perfusion clearly in rabbits.