CA2112905A1 — Ultrasmall non-aggregated porous particles entrapping gas-bubbles

USPTO Abstract

Ultra-small, substantially non-aggregated, non-crystalline particles of predetermined uniform size wich, when suspended in a liquid, contain entrapped gaseous bubbles are disclosed. These gaseous bubble particles are prepared by simultaneous co-precipitation of two compounds wherein one compound is substantially more soluble than the other in a given vehicle. When this vehicle is used for washing the co-precipitated particles, part of the soluble material is dissolved leaving a porous matrix. The porous particles then are dried and stored. The porous particles, which can be resuspended immediately prior to use, contain entrapped gas in the evacuated crevices or pores which is not displaced for a period of time because of surface tension of the suspending vehicle. The ultrasmall porous particles can be used as ultrasound contrast agents, such as ultrasound contrast agents in the blood vessels and soft tissue, including the liver, spleen, heart myocardium, kidney and brain of an animal, such as a human. The ultrasmall porous particles also can be used dry for applications where reduced weight is desirable.