Ultrasonic contrast agents, processes for their preparation and the use thereof as diagnostic and therapeutic agents

A process for the preparation of an ultrasonic contrast agent composed of microparticles which contain a gas and a polyamino-dicarboxylic acid-co-imide derivative of the formula I ##STR4## in which n is 1 or 2

• x is 1 to 500
• y is 1 to 500, where
• x+y is 2 to 1000, and
• R is O--R.sup.1 or NH--R.sup.2, in which R.sup.2 is H, (CH.sub.2)m--OR.sup.1, (CH.sub.2)m--O--C(O)--R.sup.1 or (CH.sub.2).sup.m --O--C(O)--OR.sup.1, and
• m is 2 to 6, and
• R.sup.1 is H, aryl, aralkyl, arylalkenyl, alkyl or C.sub.3 -C.sub.8 -cycloalkyl or a biologically inactive steroid alcohol or an amino acid, where aryl is unsubstituted or is substituted by C.sub.1 -C.sub.4 -alkyl, C.sub.2 -C.sub.4 -alkyl, C.sub.2 -C.sub.4 -alkenyl, C.sub.1 -C.sub.4 -alkylcarbonyloxy, C.sub.1 -C.sub.4 -alkoxy-carbonyl, C.sub.1 -C.sub.4 -alkoxy or hydroxyl,
• where the alkyl radicals specified for R.sup.1 have 1-22 carbon atoms and the alkenyl radicals have 2-22 carbon atoms, which are not interrupted or are interrupted by a carbonyloxy or oxycarbonyl group, where the repeating units placed in square brackets are distributed randomly and/or in blocks in the polymer, and where both the repeating units labeled with x and those labeled with y are identical or different and where the amino acids are .alpha.- and/or .beta.-linked, which process comprises:
• (a) a solution of one or more polyamino-dicarboxylic acid-co-imide derivatives of the formula I or a solution of this or these derivatives which additionally contains one or more other polymers and/or physiologically acceptable auxiliaries being spray-dried, or
• (b) one or more polyamino-dicarboxylic acid-co-imide derivatives of the formula I being dissolved in a solvent or solvent mixture with high melting point, or these derivatives being mixed with one or more other polymers and/or physiologically acceptable auxiliaries and dissolved in a solvent mixture with high melting point and then added dropwise to a condensed cold gas and subsequently the solvent being removed, or
• (c) one or more polyamino-dicarboxylic acid-co-imide derivatives of the formula I being dissolved in a solvent or solvent mixture and subsequently, where appropriate after addition of another solvent and/or of one or more other polymers, being precipitated or dispersed in water, and the resulting suspension being freed of solvents.