title: Nitrogen-filled liposomes as a vascular US contrast agent: preliminary evaluation.
abstract: Liposomes with a mean diameter of 1-2 microns were made to entrap nitrogen gas and tested as an ultrasound (US) contrast agent. The gas-filled liposomes, or Aerosomes (ImaRx Pharmaceutical, Tucson) were tested in vitro for size, stability, reflectivity, and acoustic characterization, and were tested in vivo for acute toxicity in mice and for cardiac imaging in rabbits after intravenous injection. Aerosomes have much greater reflectivity and higher attenuation than do standard liposomes and retain their acoustic properties after storage in aqueous media for several months. The interpolated median lethal dose of Aerosomes is approximately 2.5 mmol of lipid per kilogram, and the imaging dose is under 5 mumol of lipid per kilogram, yielding a potential therapeutic index of over 500 to 1. Postcontrast US images showed sustained enhancement of all four cardiac chambers as well as enhancement in the aorta, vena cava, and hepatic veins. Aerosomes hold promise as a contrast agent for cardiac and blood-pool imaging. Further work is in progress to characterize and develop this novel US contrast agent.
authors.affiliation: Department of Radiology/Magnetic Resonance Imaging, University of Arizona Health Sciences Center, Tucson 85724.
authors.forename: E C
authors.initials: EC
authors.lastname: Unger
authors.forename: P J
authors.initials: PJ
authors.lastname: Lund
authors.forename: D K
authors.initials: DK
authors.lastname: Shen
authors.forename: T A
authors.initials: TA
authors.lastname: Fritz
authors.forename: D
authors.initials: D
authors.lastname: Yellowhair
authors.forename: T E
authors.initials: TE
authors.lastname: New
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000032:analysis / Q000633:toxicity; D000162:Acoustics; D000818:Animals; D001769:Blood; D003287:Contrast Media / Q000008:administration & dosage*; D004337:Drug Carriers; D004452:Echocardiography; D007089:Image Enhancement; D007275:Injections, Intravenous; D007928:Lethal Dose 50; D008081:Liposomes / Q000032:analysis / Q000737:chemistry / Q000633:toxicity; D008099:Liver / Q000000981:diagnostic imaging; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009584:Nitrogen / Q000008:administration & dosage*; D010316:Particle Size; D011817:Rabbits; D013499:Surface Properties; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D003287:Contrast Media; D004337:Drug Carriers; D008081:Liposomes; D015060:1,2-Dipalmitoylphosphatidylcholine; D009584:Nitrogen