A gas emulsion forming composition comprising a dry, hollow, particulate, approximately microspherical material permeated with a gas or gas mixture, which upon dissolution in aqueous liquid forms a gas emulsion comprising a plurality of bubbles surrounded by a layer of at least a first and a second surfactant, wherein the first surfactant consists essentially of a phospholipid or mixture of phospholipids having at least one acyl chain which comprises at least 10 carbon atoms, and comprising at least about 5% w/w of total surfactant, and wherein the second surfactant may or may not be a phospholipid and is more water soluble than the first surfactant; kits for preparing such microbubbles; and methods for using such microbubbles as contrast agents.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of Ser. No. 09/013,357, filed Jan. 26, 1998, now U.S. Pat. No. 6,280,705 which is a continuation of Ser. No. 08/395,680, filed Feb. 28, 1995 and now U.S. Pat. No. 5,798,091, which is a continuation-in-part of U.S. application Ser. No. 08/284,083, filed Aug. 1, 1994 and now U.S. Pat. No. 5,605,673, which is a continuation-in-part of U.S. application Ser. No. 08/099,951, filed Jul. 30, 1993, now abandoned.
