Abstract: Liposomes suitable as ultrasound contrast agents which contain media of various types including gases, gaseous precursors activated by pH, temperature or pressure, as well as other solid or liquid contrast enhancing agents, are described. Methods of using the same as ultrasound contrast agents are also disclosed. The present invention also comprises novel methods for synthesizing liposomes having encapsulated therein gases.

Abstract: The present invention provides new and structurally diverse compositions for diagnostic imaging comprising compounds of the general formula: ##STR1## wherein A is N or CR.sub.1, R.sub.1 is hydrogen, C.sub.1 -C.sub.8 alkyl, or C.sub.6 -C.sub.10 aryl, where the alkyl or aryl group may be optionally substituted with one or more hydroxy, C.sub.1 -C.sub.8 alkyl, C.sub.1 -C.sub.8 hydroxyalkyl, C.sub.1 -C.sub.8 alkoxy, C.sub.6 -C.sub.10 aryl, C.sub.6 -C.sub.10 hydroxyaryl, C.sub.6 -C.sub.10 aryloxy, --CO.sub.2 R.sub.2, --CONR.sub.3 R.sub.4, or NR.sub.3 R.sub.4 ; D is O, --O(CH.sub.2).sub.2 O--, --O(CH.sub.2).sub.3 O--, or NR.sub.5 ; E is O, --O(CH.sub.2).sub.2 O--, --O(CH.sub.2).sub.3 O-- or NR.sub.6 ; F is O, --O(CH.sub.2).sub.2 O--, --O(CH.sub.2).sub.3 O-- or NR.sub.7 ; R.sub.2 -R.sub.7 are as defined within; g, h, i, j, k and m may be the same or different and are an integer from one to about six; X is --CO.sub.2 H, --PO.sub.3 H.sub.2, --SO.sub.3 H or --CONHOH.