Gaseous microparticles for ultrasonic diagnosis and process for their production

Process for the production of gaseous microparticles for ultrasonic diagnosis, whose wall material is built up from block copolymers of polyesters of α, β-, or γ-hydroxycarboxylic acids with linear or star-shaped polyethylene glycols and liquid crystals or from polyesters of α-, β-, or γ-hydroxycarboxylic acids and liquid crystals, wherein the desired polymer, and optionally a surface-active substance are dissolved in an organic solvent or solvent mixture, of which at least one solvent is readily water-miscible, then a gaseous perfluoro compound or water is dispersed in this solution at body temperature and them this dispersion is dispersed in water that contains a surface-active substance using a stirring mechanism, whereby the solvent is removed by pumping in gas and applying a vacuum, and finally the suspension that is thus obtained is mixed with a suitable pharmaceutically acceptable cryoprotector and freeze-dried.