| 摘要 |
It has been discovered that microparticles formed from natural or synthetic polymer with thicker walls have significantly enhanced echogenicity as compared with microparticles having thinner walls. The effec t 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 n m, although wall thicknesses from about 20 nm to in excess to 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 for 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 lumen s. Preferred polymers are polyhydroxy acids such as polylactic acid-co-glycolic acid, polylactide or polyglycolide, most preferably conjugated to polyethylene glycol or other materials inhibiting uptake by the reticuloendothelial system (RES). The microspheres may be used in a variety of ultrasound imaging applications including cardiology applications, blood perfusion applications as well as for organ and peripher al vein imaging.
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