Radiopaque liposomes: a promising new contrast material for computed tomography of the spleen.

Radiopaque, positively charged liposomes were made from lecithin, cholesterol, and stearylamine and carried diatrizoic acid salts (Renografin). Following intravenous administration of radiopaque liposomes in rats and rabbits, the spleen had the highest iodine concentration and was opacified on CT images. Contrast concentrations peaked at 30 minutes and gradually declined over a period of 24 hours. At 30 minutes, spleen CT values in rats had increased by 2.9 HU for each milligram of injected iodine (4 mg I/kg); maximum values were more than 6 times those obtained with an equivalent amount of Renografin alone. Peak spleen CT numbers of over 100 HU were consistently achieved following injections of 133 mg I/kg of opaque liposomes in rats. No acute toxicity was observed. These new contrast agents seem promising for CT of the spleen.