Stable microbubble precursors

Abstract

A microbubble preparation formed of a plurality of microbubbles comprising a first gas and second gas surrounded by a membrane such as a surfactant, wherein the first gas and the second gas are present in a molar ration of from about 1:100 to abut 1000:1, and wherein the first gas has a vapor pressure of at least about (760—X) mm Hg at 37° C., where x is the vapor pressure of the second gas at 37° C., and wherein the vapor pressure of each of the first and second gases is greater than about 75 mm Hg at 37° C.; also disclosed are methods for preparing microbubble compositions, including compositions that rapidly shrink from a first average diameter to a second average diameter less than about 75% of the first average diameter and are stabilized at the second average diameter; methods and kits for preparing microbubbles; and methods for using such microbubbles as contrast agents.

What is claimed is:  
     
         1 . A microbubble precursor composition comprising a fluorocarbon gas osmotic agent dispersed in a plurality of spray dried microspheres having an average diameter of less that about 100 μm said spray dried microspheres comprising a surfactant in combination with a compound selected from the group consisting of starch, derivatized starch, dextrin, and sugar esters having a component with a hydrophilic/lipophilic balance of less than about 8.