Gas mixtures useful as ultrasound contrast media, contrast agents containing the media and method

An injectable ultrasound contrast agent comprising of a suspension of gas filled microbubbles or microballoons in a physiologically acceptable aqueous carrier comprising usual surfactants, additives and stabilisers, wherein the gas is a gas mixture of at least two biocompatible gases A and B in which at least one gas (B) present in an amount of between 0.5-41% by vol. has a molecular weight greater than 80 daltons and solubility in water below 0.0283 ml per ml of water at standard conditions, the balance of the mixture being gas A.

A dry formulation comprising surfactants, additives and stabilisers stored under a mixture of substances which at the body temperature are biocompatible gases, at least one of which is a fluorine-containing gas whose molecular weight is greater than 80 daltons, and whose solubility in water is below 0.0283 ml per ml of water at standard conditions, the fluorine-containing gas being present in the mixture in an amount between 0.5-41% by vol., the balance 59-99.5% by vol. being air, oxygen, nitrogen, carbon dioxide or mixtures thereof.

A two component kit comprising, as the first component, a dry formulation of surfactants, additives and stabilisers stored under a mixture of substances which at body temperature are gases and, as the second component a physiologically acceptable carrier liquid which, when admixed with the first component, provides, as a suspension of the two components, an ultrasound contrast agent, in which at least one of the gases in the mixture is a fluorine-containing biocompatible gas whose molecular weight is greater than 80 daltons and whose solubility in water is below 0.0283 ml of gas per ml of water at standard conditions, wherein the gas is fluorine-containing biocompatible gas and is present in the mixture in an amount of between 0.5-41% by vol., the balance being air, oxygen, nitrogen, carbon dioxide or mixtures thereof.

A method of imaging organs in a living body, said method comprising the steps of:

• (1) administering to said body an ultrasound contrast agent comprising of a suspension of gas filled microbubbles or microballoons in a physiologically acceptable aqueous carrier comprising surfactants, additives and stabilizers, wherein the gas is a gas mixture of at least two biocompatible gases A and B in which at least one gas (B) present in an amount of between 0.5-41% by vol. has a molecular weight greater than 80 daltons and solubility in water below 0.0283 ml per ml of water at standard conditions, the balance of the mixture being gas A;
• and
• (2) subjecting said body to ultrasound therapy.