Contrast agents comprising gas-containing or gas-generating polymer microparticles and/or microballoons, in which the polymer is a biodegradable polymer containing units of formula --(O).sub.m --CO--O--C(R.sup.1 R.sup.2)--O--CO--(O).sub.n -- (wherein R.sup.1 and R.sup.2 each represent hydrogen or a carbon-attached monovalent organic group or together form a carbon-attached divalent organic group, and m and n are each independently zero or one) may be used in diagnostic applications such as ultrasound and MR imaging.
对比剂包括含气或产气聚合物微粒和/或微气泡,其中聚合物是含有式单元的可
生物降解聚合物 --(O).sub.m --CO--O--C(R.sup.1 R.sup.2)--O--CO--(O).sub.n --(其中R.sup.1和R.sup.2分别代表氢或碳连接的一价有机基团,或者一起形成碳连接的二价有机基团,m和n各自独立地为零或一),可用于诊断应用,如超声和磁共振成像。