Abstract: A diagnostic method analyses the effect of intervention, e.g. by surgery, especially in the myocardium. (i) Hollow microcapsules are administered into a blood vessel of a patient having a perfusion defect, (ii) if desired, an ultrasonic image is formed of the tissue, (iii) the occlusion is at least partially removed such that the blood flow in at least one area of the tissue is increased, and (iv) an ultrasonic image of the tissue is obtained after treatment. This is based on the observation of the particular properties of the microcapsules in the myocardium. It is also the basis of providing appropriate drugs to that site.

Abstract: Microspheres are prepared by a process comprising the steps of (i) spray-drying a solution or dispersion of a wall-forming material in order to obtain intermediate microspheres and (ii) reducing the water-solubility of at least the outside of the intermediate microspheres. Suitable wall-forming materials include proteins such as albumin and gelatin. The microsphere have walls of 40-500 nm thick and are useful in ultrasonic imaging. The control of median size, size distribution and degree of insolubilization and cross-linking of the wall-forming material allows novel microsphere preparations to be produced. In particular, the microspheres may be 15-20 .mu.m, targeted to selected areas of the body or of prolonged life in the circulation.

Abstract: A sterile powder comprising microparticles, 0.1 to 50 .mu.m in diameter, obtainable by spray-drying and cross-linking a water-soluble material having free functional groups, is characterized in that the microparticles are hydrophilic, can be reconstituted in water to give a monodisperse suspension, and have retained said groups available for derivatization. The particles are linked to drugs or other functional molecules, and used as vehicles in therapy.

Abstract: A process for forming microcapsules comprising (i) providing a solution of a protein in an aqueous solvent and (ii) spraying the said solution into a gas such that the aqueous solvent evaporates, thereby forming hollow microcapsules, characterised in that the aqueous solution contains a liquid of greater volatility than water.The protein is preferably albumin and the volatile liquid is preferably ethanol.The microcapsules may be used as ultrasound echogenic contrast agents.