Vascular X-ray contrast media comprise ferrite powder coated with a negatively charged colloid such as silicate colloid, gold colloid, silver colloid or platinum colloid. Such media can be used for the medical X-ray diagnosis of small blood vessels. By applying an external magnetic field, the media can...http://www.google.de/patents/US4101646?utm_source=gb-gplus-sharePatent US4101646 - Ferrite vascular contrast media
