Physicochemical characteristics of Sonazoid, a new contrast agent for ultrasound imaging.

The objective of the current work is to describe the physicochemical characteristics of Sonazoid, a new ultrasound contrast agent for detection and characterisation of focal liver lesions. It has been demonstrated that Sonazoid powder for injection consists of microspheres of perfluorobutane (PFB) stabilised by a monomolecular membrane of hydrogenated egg phosphatidyl serine, embedded in an amorphous sucrose structure. Upon reconstitution with sterile water, stabilised microspheres of PFB are released in a predefined amount and size into a low viscosity, isotonic sucrose solution with a neutral pH. Sonazoid reconstituted product contains approximately 8 microl microspheres/ml with volume median diameter of approximately 2.6 microm. The product contains approximately 1.2 billion microspheres/ml of which less than 0.1% are larger than 7 microm. The acoustic properties of Sonazoid such as attenuation efficacy, fundamental and second harmonic backscatter efficacy are all well correlated to the microsphere volume concentration. The stability of Sonazoid after reconstitution is good, with no significant changes in physicochemical properties 2 h after reconstitution. Pressure stress is well tolerated by both concentrated and diluted Sonazoid with no permanent effects of pressures up to 300 mm Hg. The level and consistency of the investigated physicochemical properties demonstrate that Sonazoid should be well suited as a contrast agent for medical imaging with ultrasound.