From Bayer Schering Pharma AG:
Sonovist® (sometimes found as Sonavist) is an investigational ultrasound contrast agent with a biodegradable synthetic capsule filled with sulphur hexafluoride. The biodegradable shell of Sonovist is so stable that it can be taken up by Kupffer cells of the reticuloendothelial system or accumulate in the sinusoids.
Therefore, Sonovist® has an additional hepato-splenic parenchymal phase following the blood pool phase, analog to the superparamagnetic iron oxide agents used in liver MRI. The microbubbles are stationary in this phase and generate no conventional Doppler signals. This tissue-specific phase has a variable duration and can be imaged by bubble specific imaging modes.

The Germany-based pharmaceutical company is the result of the take-over of Schering AG by Bayer AG in 2006. The Bayer Schering Pharma AG is part of the Bayer HealthCare AG, which represents the pharmaceutical part of the Bayer Group.
The company makes ultrasound, x-ray and MRI contrast media, drugs for treating cancer, multiple-sclerosis, heart and nervous system disorders and severe skin conditions.
In general, its activities are focused on four business areas: Fertility control & hormone therapy, diagnostics & radiopharmaceuticals, dermatology as well as specialized therapeutics for disabling diseases in the fields of the central nervous system, oncology and cardiovascular system.
Currently, Bayer Schering Pharma discontinued the manufacturing and development of ultrasound contrast agents.

Ultrasound Contrast Agents: