Abstract: It has been discovered microparticles formed from natural or synthetic polymer with thicker walls have significantly enhanced echogenicity as compared with microparticles having thinner walls. The effect of wall thickness has been determined experimentally as well as inserted into a formula for use in predicting the optimum conditions. In the preferred embodiment, the polymers are synthetic biodegradable polymers and the wall thickness is between about 100 and 660 nm, although wall thicknesses from about 20 nm to in excess of 500 nm can be used. The microparticles are manufactured with a diameter suitable for the targeted tissue to be imaged, for example, with a diameter of between 0.5 and 8 microns for intravascular administration, and a diameter of between 0.5 and 5 mm for oral administration for imaging of the gastrointestinal tract or other lumens.

Abstract: It has been discovered that the incorporation of gases, especially fluorinated gases such as perfluorocarbons, into microparticles formed from the combination of a natural or synthetic polymer and lipid have significantly enhanced echogenicity as compared with microparticles not including the lipid. Compounds other than lipids which are hydrophobic and limit the penetration and/or uptake of water into the microparticles can also be incorporated into the microparticles to enhance echogenicity. In the preferred embodiment, the polymers are synthetic biodegradable polymers. The microparticles are manufactured with a diameter suitable for the targeted tissue to be imaged, for example, with a diameter of between 0.5 and 8 microns for intravascular administration, and a diameter of between 0.5 and 5 mm for oral administration for imaging of the gastrointestinal tract or other lumens.

Abstract: A system for reducing post-cardiopulmonary bypass encephalopathy due to microembolization of the brain of a patient with gaseous microbubbles (less than 40 microns in diameter) occurring during open-heart surgery using a cardiopulmonary bypass machine by passing a stream of blood from the patient through an ultrasonic traveling wave which propagates across the stream without reflection and sweeps the blood clean of the microbubbles without inducing blood cell trauma. The blood passes through a chamber between an input port and a filtrate exit port. An ultrasonic beam is projected so that a pressure maximum of the main lobe of the beam is centered at the filtrate exit port. The microbubbles are carried by the traveling wave to a waste exit port in the chamber downstream of the input port.