DISSOLUTION OF MULTICOMPONENT MICROBUBBLES IN THE BLOOD-STREAM - 2 - EXPERIMENT

The effect of the nature of the filling gas on the persistence of micr obubbles in the bloodstream was studied. All the microbubbles were cov ered with the same shells. Various perfluorocarbons and perfluoropolye thers alone and as mixtures with nitrogen were used as the filling gas es. The persistence time of microbubbles in the bloodstream tau increa sed with the molecular weight of the filling gas, from similar to 2 mi n for perfluorethane, to >40 min for perfluorodiglyme, C6F14O3, and th en decreased again to 8 min for C6F14O5. An acceptable ultrasound scat tering efficacy was exhibited by the filling gases with intermediate m olecular weights that possessed both a high saturated vapor pressure a nd a comparatively low water solubility (Ostwald coefficient). On the basis of the experimental data, it is concluded that the microbubble p ersistence tau is controlled primarily by the dissolution of microbubb les and not by the removal of the microbubbles by the reticular endoth elial system. Although the qualitative experimental trends are in good agreement with the theoretical model developed previously, there are some quantitative differences. Possible reasons for these differences are discussed. (C) 1998 World Federation for Ultrasound in Medicine & Biology.