Coarse dispersed systems as ultrasound contrast media

The objective of this in vitro study was to develop and characterise coarse dispersions as ultrasound contrast media for incontinence diagnostics. Sus pensions were formulated by adding 1% (w/w) of water insoluble particles (b arium sulphate for suspension, compound tragacanth powder, light kaolin) an d different concentrations (0.05-1.5% (w/w)) of the sugar ester Crodesta(R) F10 (sucrose distearate) to 5.5% glucose-solutions. Milk and Intralipid(R) were used as emulsions. The dispersions (100 ml) were filled into balloons and insonated in a waterbath. Video images were analysed for echogenicity of the dispersions in the balloons. Particle size measurements of the dispe rsions and true density measurements of the particles were performed. Suspe nsions of barium sulphate (mean particle size x = 8.1 mu m, relative densit y rho(rel) = 4.5) initially produced high echogenicity. Echogenicity rapidl y decreased to produce a non-echogenic dispersion after approximately 10 mi n, due to sedimentation of the solid particles. Light kaolin suspensions (x = 2.7 mu m, rho(rel) = 2.73) were only weakly echogenic. Compound tragacan th suspensions produced strong echogenicity, but sedimentation of the relat ively large particles (x = 150.0 mu m, rho(rel) = 1.6) occurred within 10 m in. The emulsions were non echogenic. Crodesta F10 (x = 45.5 mu m, rho(rel) = 1.04) produced suspensions of high and sustained (>30 h) echogenicity in concentrations between 0.01 and 1.5% (w/w) because of their sufficiently h igh particle size and very low sedimentation velocity. Coarse suspensions ( but not emulsions) may produce quantitatively and qualitatively good and la sting echogenic properties. The formulation of a technologically simple, lo w-cost ultrasound contrast medium for incontinence diagnostics seems feasib le.