Stabilized microbubble compositions for ultrasound

A microbubble preparation formed from a plurality of microbubbles, comprising a first gas and a second gas enclosed by a membrane and a surfactant, WHERE THE FIRST AND SECOND GAS IS PRESENT IN AN INDEX MOLAR from about 1: 100 1000 : 1, and wherein the first gas has a vapor pressure of at least about (760 -X) MM HG at 37 degrees C, where x is the vapor pressure of the second gas at 37 degrees C, AND WHERE THE VAPOR PRESSURE EACH OF THE TWO GASES is greater than about 75 mm Hg at 37 degrees C; ALSO SHOWN methods for preparing microbubble compositions, INCLUDING QUICKLY compositions dwindle from a first diameter SECOND HALF TO A LESS THAN 75% OF FIRST APPROXIMATELY DIAMETER AND stabilize in the second diameter; METHODS AND EQUIPMENT TO PREPARE microbubbles; AND MICROBUBBLE methods of using such as contrast agents.