Contrast agents

Abstract

Contrast agents comprising microbubble-generating carbohydrate microparticles having a surfactant admixed within the microparticulate structure, with the proviso that the surfactant is not a C 10-20 fatty acid, are disclosed. Processes for preparing contrast agents also are disclosed.

1 . A contrast agent comprising microbubble-generating carbohydrate microparticles having a surfactant admixed within the microparticulate structure, with the proviso that the surfactant is not a C 10-20  fatty acid.  
     
     
         2 . A contrast agent as claimed in  claim 1  in which the carbohydrate is a water-soluble pentose, hexose, disaccharide, polysaccharide or sugar alcohol.  
     
     
         3 . A contrast agent as claimed in  claim 2  in which the carbohydrate is galactose.  
     
     
         4 . A contrast agent as claimed in any of the preceding claims in which the surfactant is selected from straight chain aliphatic carboxylic acids and salts, sorbitan esters and mono- and di-glycerides thereof; aralkanoic acids and salts thereof; steroid acids; sterols; straight chain aliphatic alcohols; phospholipids; alkali metal alkyl sulphates and sulphonated esters; polyoxyethylene-polyoxypropylene copolymers; polyoxyethylated sorbitan esters and mixtures of any of the foregoing.  
     
     
         5 . A contrast agent as claimed in any of the preceding claims in which the surfactant comprises a lipophilically modified carbohydrate.  
     
     
         6 . A contrast agent as claimed in any of  claims 1  to  4  in which the surfactant comprises carbohydrate- containing liposomes.  
     
     
         7 . A contrast agent as claimed in any of the preceding claims in which the surfactant is present in an amount of 0.1-2.0% w/w relative to the microparticulate carbohydrate.  
     
     
         8 . A contrast agent as claimed in any of the preceding claims in which the microparticles are aggregates having an aggregate size of 30-50 micrometres of microparticles having a particle size of 1-10 micrometres.  
     
     
         9 . A process for preparing a contrast agent as claimed in  claim 1  which comprises (i) either mixing solutions of the carbohydrate and surfactant and removing the solvent(s) therefrom or mixing a solution of the carbohydrate with a liposome-forming material and removing the solvent therefrom and (ii) micronising the resulting mixture to yield the desired microparticles.  
     
     
         10 . A process as claimed in  claim 9  in which the mixture is micronised by ball-milling.  
     
     
         11 . Use of a contrast agent as claimed in any of  claims 1  to  8  in diagnostic imaging.  
     
     
         12 . Use of a contrast agent as claimed in any of  claims 1  to  8  in diagnostic ultrasonic imaging.  
     
     
         13 . Use of a contrast agent as claimed in any of  claims 1  to  8  in magnetic resonance imaging.