Patent ID: 6139818
Filing Date: 2000-10-31
Classification: A61K

Abstract:
A method of making ultrasonic contrast agent useful in ultrasonic imaging of human or animal patients comprising a suspension of gas filled microballoons, with a mean size in the range from a fraction of micron to 1,000 microns, in an aqueous carrier liquid, the method comprising the steps of:(1) emulsifying a hydrophobic organic phase into a water phase so as to obtain droplets of said hydrophobic phase and an oil-in-water emulsion in said water phase;(2) adding to said emulsion a solution of at least one polymer in a volatile solvent insoluble in the water phase, so that a layer of said polymer will form around said droplets;(3) evaporating said volatile solvent so that the polymer will deposit by interfacial precipitation around the droplets which then form beads with a core of said hydrophobic phase encapsulated by a membrane of said polymer, said beads being in suspension in said water phase;(4) subjecting said suspension to reduced pressure under conditions such that said encapsulated hydrophobic phase is removed by evaporation;wherein said hydrophobic phase is selected so that it evaporates substantially simultaneously with the water phase and is replaced by a gas other than air, whereby dry, free flowing, readily dispersible microballoons with an envelope thickness ranging from 50-500 nm are obtained, and(5) suspending the dry, free flowing, gas microballoons in an aqueous carrier liquid.