Preparing hollow microcapsules.

A process of preparing microcapsules consisting of (i) providing a solution of a protein in an aqueous solvent and (II) vaporizing said solution to convert it into a gas so that the aqueous solvent evaporates, forming Hollow microcapsules characterized by CONTAIN A LIQUID AQUEOUS SOLUTION MORE volatile than water. PROTEIN AND IS PREFERABLY ALBUMINA volatile liquid is preferably ethanol. Microcapsules can be used as echogenic contrast agents ULTRASOUND.