HIGHLY CONCENTRATED 1,2-BIS(PERFLUOROALKYL)IODOETHENE EMULSIONS FOR USE AS CONTRAST AGENTS FOR DIAGNOSIS

New 1,2-bis(F-alkyl)-1-iodoethenes, CnF2n+1CH=ClCn'F2n'+1 (Fnn'IE), ha ve been evaluated as to their emulsifying ability for use as contrast agents. Highly concentrated (up to 90% w/v), heat-sterilizable emulsio ns were obtained with egg yolk phospholipids (EYP) as surfactant, with both small average particle sizes and narrow size distributions. The emulsions prepared from Fnn'IE with n+n' = 10 were more stable at 40 d egrees C than those with n+n' = 8. The latter were stabilized by repla cing a small amount (similar to 3% w/v) of Fnn'IE by an iodinated mixe d hydrocarbon/fluorocarbon molecule CnF2n+1CH=CICmH2m+1 (FnHmIE) actin g as a molecular dowel, without any adverse conse quence on the radiop acity. Phase separation occurred, however, in all cases after about tw o months at 40 degrees C. The in vitro radiopacity of these emulsions is, for the same concentration, three- to four-times larger than that of perfluoro-octyl bromide. However, a decrease in pH during heat-ster ilization and upon ageing, which compromised their use in vivo, was ob served.